Am I Gay? I need advice!

Well here's the deal, I'm 18. When i was a bit younger i found gay porn, and i watched it alot. I liked it. Now I fantasize about having sex with others guys, bottoming , watching more types of porn (lol). The thing is i find girls sexy and attractive, whereas men I don't. I cant even picture myself kissing another man, only having sex. I've always wanted to have girlfriend too.Eventually I even started looking at the m4m/t4m sections on craiglist, even posting but discretely. I eventually scheduled to meet up with a person i found. When i went to meet him, i was scared. When i got in the car i got so nervous and scared, i eventually told him, i couldn't do it, because it didnt feel like i really wanted to do it.. He was nice, that he understands and dosnt force, he dropped me off and i left.I don't know waht to do, am i gay, bi, straight? Should i go and try again, or is all this cuz im a horny teen with fantasies (lol)?