Eating Disorder or what?

I haven't been able to eat for three days now. Whenever I think about food i start feeling nauseated. If i do try to eat I end of feeling incredibly sick but I don't think it's a virus because i never actually throw up. I have recently been very unhappy with my weight so the thought crosses my mind that this would be a good reason to not eat-lose weight.... Now I don't like the pain I get and I don't think I'm bulimic because I don't want to throw up. I don't think I'm anorexic either because though I know I'm overweight I dont want to be too skinny. I have no idea what caused the nauseau but I'm worried about my reaction to it more. Help?