Research glycogen loading. 3 pounds of water can be dropped in a hour, or even more if your carb depleting.
If you lose about 1.5 pounds per week, you're on track. 3 pounds of lard is a lot of calories, and likely you haven't lost that. Likely, you just de-loaded glycogen a bit, and / or your electrolyte levels are a bit different than before.
Remember: you didn't get to be fat and ugly overnight. It will take time to undo the damage, and to begin to recover. You need to lose 1.5 pounds week after week for some time. Some weeks, you might lose .5 pound, another week 1 pound, or even gain another. You have to look at the trends instead of the instant gratification. Remember: that instant gratification is what got you in this mess to begin with. Think big picture for success.
That's part of the problem, understand, in why you're as you are: impatience; instant gratification. You have to alter your mindset to look long-term, at the big picture, with a focused, patient, plan for success. Remove yourself from situations where you'll mess up your plan, and then make bullshit excuses for why you suck. Set yourself up for success.
I can load about 7 pounds of water overnight if I'm carb-depleted. This has to do with how glucose, oxygen, and water bind in your muscles, and in your liver. You can read all about it on Wikipedia, or any of a number of excellent bodybuilding boards.
Many fat folks lose the glycogen and think they're on track, when in fact, they've depleted carbs. Next week, if you're only down another pound, that would be expected, and the key to success is discipline (controlling those digits, eating on time, and the right things), and patience. It will take time and 1.5 to 2 pounds a week, if you're depleted, would be on track.
Number one thing, learn the power of the mind. Continue to tell yourself, "I will not eat myself to death" whenever you're inclined to make bad choices.
Don't associate with fat folks which will cause you to lose discipline. Once you're in better health, you can renew those relationships if need be, but, for now, it's best to stay away from them, and their lifestyles. We're talking about saving your life here, and that needs to become your central focus. It's simply mind over digits. It's not rocket science.
If you gain a pound, don't sweat it. It's likely just some water. I drop about .8 pounds every time I go #1. Check it sometime, and you'll see I'm right.
You have to learn to think of yourself first, in longer time spans, patience, in methodically executing a plan.
As you stay away from old habits, and those that promote them, and engage in a more winning (towards saving your life) ways, hopefully, your habits will change and they'll become automatic.
Stay away from the wrong environments / people.
Look at the big picture.
Put your mind in charge of your digits.
Come to view food as a function, rather than as a medication.
Every time someone or something tempts you, tell yourself "I'm better than this, and I'm tired of being a fat slob, and I'm not eating that crap." After a while, it'll become a habit, and your body will change.
Remember, also, you are in complete control. No one forces you to eat junk. Now, it's simply a matter of taking charge, changing your habits, and giving it some time. YOU WILL FAIL, HOWEVER, IF YOU DO NOT CHANGE HOW YOU VIEW FOOD, AND YOU DO NOT LEARN NEW HABITS.