I've been thinking about this question ever since I saw your topic--for myself as well.
The first thing you need is to get your Dr. to put you on testosterone, the more the better. Test has been shown to turn even the clumsiest most ignorant and irritating moron into a totally self confidant asshole who believes he's gods gift to humankind, even though it may also make him even clumsier, more ignorant and irritating than he was before.
Obviously I'm (sort of) joking about the testosterone thing. The point is, being self-confidant doesn't necessarily make one a better human being. For sure, some of us need more self confidence than we have. For whatever reason we're so caught up in thinking about what other people *may* be thinking about us, almost all of which shows us to ourselves in a less than positive light, that we fail to see that *most people* seldom think of us *at all* and, even when they do, the thought of us pails in comparison to their own thoughts about themselves, whatever they may be.
So, besides chemistry, what builds self confidence? Well *one* thing is the ability to do something well. It doesn't really matter what it is. So, my first suggestion is you sit down with a piece of paper (far better than doing it on a computer or device, IMO, because you can hold it in your hand, fold it up, stick it in your pocket, carry it around with you as a reminder or, alternately, pin it on a door or something where you can see it repeatedly), and write down in big capital letters: DANNY IS REALLY GOOD AT _______________! (fill in the blank).
Whatever it is, the point is, you *know* this about yourself. It doesn't matter that much (although, admittedly, it does help) whether anyone knows it or acknowledges it. What matters most is that *you* know it.
Another way to build confidence is to *become* good at something you're not good at now. Again, doesn't matter what it is. It does help if it is something that interests you but it doesn't have to be a major life accomplishment like sky-diving or becoming a brain surgeon. Can be something simple but just generally ignored. For example, you decide that for the next week when ever you go out of the house you're going to wear something *you* feel makes you look good, or sexy, or confident, or attractive or whatever. Like I say, that's just an example, can be anything but it really helps to set yourself a *reachable* goal of some sort and then actually carry that through.
Another example sort of like the above is to do dead lifts. First, research online and find out the *proper* way to do them. Focus on learning the *skill* and *form* of dead lifting and concentrate on that. When you go to the gym it may be you will *only* do this one thing (you can give yourself permission to do this). Forget about all the rest of it for the time being: You're going to become a master dead lifter! Take pencil and paper with you and keep very accurate notes on: a) how much you lifted; b) how many reps/sets; c) the length of time you did the reps/sets. Before you begin, make note of how you were feeling (no matter what you were feeling, just your overall mood, how apprehensive you may be feeling or w/e). After the workout, again, make note of your mood, whatever it is (happy, excited, discouraged, annoyed or w/e).
After dong this every other day for a week or so, (and rewarding yourself with good food, especially some protein, immediately after your workout), begin to set yourself goals. You now have an objective record of what you *can* do. Now, you're ready to begin challenging yourself. Not *too* much, just enough. That could mean a) adding more weight to the bar; b) doing more reps or sets; c) doing the same weight, reps/set but in faster time (but still in perfect form). It may be one week you'll choose a, the next, b, and the third c; always aiming to make each workout your own *personal best*. It doesn't matter one damn bit what *anyone* else around you is doing or what they may be thinking about what *you* are doing. For get that! You're there doing what you are doing *for yourself* and only for yourself.
Seriously, try that for, oh, I duno, a couple months or so and observe what happens. I can pretty much guarantee that, although obviously it isn't going to take care of all your self-worth / self-confidence issues, it will make a dent. Hey, it will naturally raise your testosterone, for one thing!
I'm someone who has struggled with those issues my whole life. The fundamental message I got (especially from my dad) was that I'd never amount to anything. He told me that directly and indirectly over and over and over again as a child. Even though a part of my mind rebelled against it and set out to prove him wrong, another part of me 'bought' it and I've struggled with it in every endeavor I've engaged in since.
BUT… and this is the point… building self confidence *begins* with acknowledging *what* we're confident about *already*. If we can do one thing well, then we can do a second thing well, and a third, and so on. It just takes focus, time, attention, practice, and, most of all, a willingness to *endure* our own inner critic *and not let him stop us* (or stop us for long).
Another thing that helps is to be mindful of your own thought processes. If you say to yourself, "I can't do it," or "I'm not good enough," or "I hate this about myself," or "I wish I were____" (fill in the blank) -- the main-stays of people with low self-esteem issues -- then well, a) you need to be aware that you're harming yourself with these thoughts and b) some part of you needs to begin standing up for you by saying, "No, I *can* do this, I *am* good enough, I *don't* hate myself, and I only wish to be *the best myself
* I can be!" See, what *matters most* is NOT what other people think of you, what matters most is what *you* think of yourself.
So, buddy, I hope this helps. I know, believe me I *know*, how hard it is especially when people around you reinforce the negative over and over again. *That* becomes our reality. BUT what I'm trying to get across is that that "reality" isn't really real. For sure we all have our weaknesses… ALL of us have faults or ways we can improve. Remember that! No exceptions there. But what other people are or aren't really isn't under our control. The only person we can change is ourselves (and, even then, often with much difficulty). BUT it *can* be done. It just takes a bit of focus, a bit of discipline and, most of all, the slowly growing awareness that, not only is there nothing wrong with us, we are made up of a *lot* of good qualities already and many more that can be improved.
You can do it. Not saying it will be 'easy'; but who values things that come 'easily'? Easy isn't the point. The point is you can face yourself, your inner contradictions, and through facing them you can reconcile them and overcome them. I'm confident of that! Soon, you will be too. ;)