I'm actually bisexual but grew up Christian, what do?

I like pussy, putting my penis in a tight hole feels good. But I've always liked getting fucked in the ass too. I bought a dildo and hid it in the basement. When my parents aren't home and my GF isn't available I like pegging myself with it until I cum. Cumming from milking my prostate just feels great.

How do I tell my gf? She's a devout Christian, and hates homosexuals I make jokes about homos when I'm around her and she always laughs.

Will she break up with me if I tell her I want to get pegged? My ultimate fetish is to get fucked in the ass while I'm fucking a pussy.