Really weak immune system?

Im 16 male. Just recovered from clinical depression, anorexia and bulimia. But put them aside. I have a really poor immune system. I'm sick every few days if not mildly weekly. It's not dietary and was wondering are there diseases or something excluding cancer that can cause really weak immune system. Also my body is weak in itself. Like I can break, bruise, etc easily. My body is like deteriorating.