I just don't know why i do this again and again

I'm an almost 18 years old guy.I guess i'm gay.. I mean i think men are attractive and 'i want one'. In every relationship in my mind i visualize myself in the girls place, so yea, i guess i'm gay. But i just can't accept that.. I always do the same thing again and again but i don't know why: i sign up on a gay internet dating site, there i always found easily a chat-partner who is handsome and intelligent, most of the time he thinks the same. so i start talking with him and after some hours i feel myself bad, shameful. like i'm making a huge mistake, i ruin my life now etc etc. the "gayfeeling" is still there, i mean i still want to be with someone but i'm too afraid of that.what should i do?? i just can't believe how loser am i, i guess people on that dating site think i'm crazy because i sign up and delete my account at least once in a week...