I am losing appetite, losing weight, have little energy, can't sleep well, and have painful stomach pains.?

It all started when I got my period, I got little appetite, and when I eat like too much then I feel like vomiting, problem is I barely ate food, I eat like 1 meal a day and it is pretty small, but I feel like I can't eat more. I feel like it could be my depression but at the same time when I do exercise I notice I get tired really easy and lose my breath easier. HELP!! :(