I just wanted to add that maybe it would be helpful to you to really think about what was making you feel ill about the encounter. For some people figuring out their sexuality is really difficult. I agree that there is a spectrum of "totally straight" to "totally gay" and a whole lot of variations on bisexual in between.
From your description, it seems like there are a few different things going on. Were you just turned off at being with a guy? Was it just feeling like doing something sexual with another guy is "wrong"? Was it the fact that you found this stranger off Craigslist? In general, do you tend to worry about STDs after a sexual encounter (some people seem to be a little obsessive or germ-phobic and get worked up after every new sex partner)?
I am female and consider myself bisexual. Whatever kind of sexual feelings you are having are OK. You don't have to make a decision NOW or definitively choose a camp immediately or anything. If you fantasize about men, fine. If you want to act on it, fine. I might worry a little more about meeting strangers for sex. That can be risky for any number of reasons, you know? Maybe hang out in areas (neighborhoods) or venues (bars, bookstores, coffeeshops) that are gay-friendly and see how you feel. It would probably feel more natural to meet someone in a setting like that, get to know them a bit. Also, pick up the local gay newspaper (lol, or is everything online nowadays?!) and see what's going on. Often there are groups or clubs, etc. you could try out to maybe meet people or find other people who are bisexual and interested in experimenting.
And, hey, if you tried it once and are completely turned off--that's fine, too.
Good luck with everything. Feel free to let us know when you get your test results back.