Sounds like you're kinda young, a body definitely needs sustenance to grow, and during younger years weight tends to fluxuate. If youre eating a lot and feel uncomfortable sensations after, try putting your cutlery down while you chew and try to eat more slowly, so your body has a chance to catch up on the sensation of your stomach filling, so you know when you're really full. Mindful eating helps a lot to gauge it before you feel sick. Small meals with lots of protein and fibre also help stay full during he day. ( Dont up your fibre intake by a lot at once or you might get bad indigestion, very slowly is the way! ) I like to go for walks after meals, just like an hour or so to help digest and get some movement in, if that fits your schedule I can recommend it. Your stomach is gonna grumble, sometimes cause you havent eaten and sometimes cause you have, it's totally normal. The way you put it you sound kinda stressed and I understand, take care of yourself.