How I become a bisexual

I had 15 years.
Saturday night at my friends crib and three of us. my friend I and some girl..we drink as usual, and then my friend put some porn..he and chick start kissing and i watched them. after she was making out with me and my friend was already naked and he was wanking already. after thaht I stand up i girl start suck on both of us.

after that we start fucking it was great two of us and drilled chick..but that is another story..
real thing was that i look at my friends cock..when girl went home, both of us stayed naked and we were drinkiing more

after 20 min i was on my all four looking for clothes when I suddenly sensed cock on my ass..few sec later that thing was in my mouth it start to feel so good and I thought ok thats it..he will cum in my mouth and we are finished.

But I was wrong, he put some lube on my ass and his cock..and when he start push him in my ass..the pain was big i could not handle it. Then he pull it out, again slide all over my ass and hard push him inside..and like savage he start fuck me..soon pain and pleasure become one and I push out my ass so he can fuck me harder..and the finally i sense him pulsing in my ass, i enjoy it. And ever since that night when we fuck some girl it was my turn to fill me up..so when I turned 18 i start to meet other mens