Eating twice a day is not a good plan for gaining muscle (or a good plan for good health in general. It is not healthy for your blood sugar to dip and rise so much. Your blood sugar levels should stay even). You really need to be eating around 5 meals a day or more (3-4 meals would be much better than just two, but as I said, you should aim for 5). I eat on average 5-6 times a day. Some days, I only manage 4 times, and even on those days I feel a bit sluggish. Very rarely do I get less than 4. If I get less than 4, I feel like absolute crap. I have no energy through the day. I'm a walking zombie.
I used to be like you (except I was really fat. My body puts on weight rather easily). I lost a lot of fat and gained muscle by eating better and eating more often.
It's been said that diet is more important than the actual workout when it comes to your body shape. I believe it. If your diet is bad, working out is not going to make a radical change in your body (unless you have some freaky genes or you are juicing).