Ok, I had ecoli 3 years ago from poorly cooked ground beef. Not fun at all. Here's what you should look for:
-EXTREME cramps; I pretty much layed in bed and cried. The pain killers I got from the doctor did NOT help.
-lots of vomitting; you eat food and then maybe 1-2 hours later you vomit it up.
-diarrhea w/ blood; even if you've vomitted up all your food, you're still going to crap blood. I crapped blood for almost 6 days (went on antibiotics 12 hours after starting).
If you think this is you, see your doctor now. If it's after hours, go to the emergency room. You need to get antibiotics ASAP. They'll take a stool sample (I gave them a bunch of blood), test it, write a presciption and send you on your way. They called me back in a few days later to get some blood taken.
Also, if this is you, you won't be eating food for the next few days. For 7 days, I didn't eat, and could only drink "clear" liquids (water, gatorade, ....).
Needless to say, it was not a fun time at all. Good luck!