I want to starve myself

I'm 20, 5"4 and 190lbd and I suffer from PCOS. I've gained 50lbs in almost two years. I can't keep it off no matter how hard I exercise (I'm really into volleyball and track) I've had my thyroid checked and everything came back good. I hardly eat most days but then there's days I just binge and I make myself throw up to not feel like a fatass. I don't know what to do anymore. I feel fucking gross.