I think im errrm... Straight

Maybe he was bad in bed.

Are you attracted to women? What made you sure you were gay?

You should understand homosexuality a bit better. You may not have liked bottoming, but you may like topping. Being gay doesn't necessarily mean you have to, for lack of a better term, "bend over" for someone. Research it a little and try your luck again. If you do decide to bottom, be sure to use the proper tools (lubrications, condoms etc.). Good Luck!

It may be that your reaction afterwards was due to a conflict in your mind regarding many years of being told that sexual attraction to a male is wrong.
Many guys go through years of torment coming to terms with being attracted to another guy. Your reaction is common, most likely a form of guilt, which has been expressed as a physical sick feeling.
You need to be totally honest with yourself and let the feelings you have be and not over analyse them.
If you find a guy attractive and there is a need to have sex with that person, then that is all the answer you need. You may go through a period of finding males attractive or even just one or two.
There is also the chance you may meet a female and you may be totally happy with that.
I posted an answer to a question on the post titled "masturbation". I think you may get a lot from my answer.
Don’t label yourself.