My appetite changed..

My bf worried cuz I haven't been eating lately much. Idk what it is like I'll eat a small portion and then I'm okay for the day but when I do eat I eat my normal amount. Every time I eat though small portion or not depending on the food it hurts my stomach and makes me nauseous. I still have period symptoms too and I've been off since the 23rd. Any idea what's going on with me? I know I need to talk to doctor but I cant make any appointments till after the 1st of the year.