Open Question: Ate some food, then felt really nauseous. Dont know what it could be.?

I had gone out earlier tonight with my friends, and had decided to go out and eat before heading back home. After I ate, I suddenly becamse very very VERY nauseous, and I felt like crap. I dont know what could have caused this...(food, nerves etc) yet why do I have the strangest feeling that something "fishy" is going on? I was dramatic enough to look up Date Rape signs (roofies) but, obviously, it wouldnt be that. Any ideas?