uality Help.........?

Okay so here's the deal, I'm 17 and I'm sure I'm either gay or bi. I don't understand why people say that gay people choose to be gay. I remember that I had a crush on a guy when I was in the FIRST grade, and I didn't even know what gay was. The problem is that my family is very religious and I don't know if I should tell them that I'm gay. I've been Catholic all my life, and I absolutely believe in and love God more than anything in the world. I go to church every Sunday, pray everyday, and do other stuff to help out the church. I also have strong morales like I don't drink, do drugs, and I want to wait until I'm married to have . I think I may be bi but only because I've been pretending my whole life that I don't like guys. I also think that my parents thought that I was gay when I was little, but as I was growing up I kept on telling them about girls that I "liked", which made them think that I'm not. Overall, I just want to finally come out, but I'm scared about what my family/friends/other people might think. What should I do?