Can straight people become gay?

I know people will throw you are born with your sexual preferences. But I beg to differ(to a degree) We have a guy here. He's straight and he hangs around gay guys. You don't think he might get curious and question himself. I myself for example hung around with my share of LGBT people and I see a big change in myself. Homosexuality is like tetris. My straightness is like the empty square and the gayness is like the blocks that fall down. From ages 11 to 18 I feel like I have peeked. 11-14 I was a homophobic idiot who would look down on gays. ages 14-16 I was still the same, but I was 50/50(bisexual) I often got angry and ashamed I was thinking about men sexually PERIOD. I kept to myself and was still belittling gays. ages 17-18 my sexual thing for women is decreasing. my gay side is getting stronger. Its more than just sex now. I say to my self daily"I guess I could try to hold a mans hand, kiss him and be romantic with men""I guess being totally gay isn't all that bad. I have been thinking like this for 4 months. I have had flashbacks to this hot 17 year old when I was 14. Hes 21 now and we dated recently. i wanted to do things to him, but my brain kinda blocked me from letting me feel that way. what is wrong with me?