You are gay or bi if you have sexual or romantic feeling towards men. Anal sex does not play a part, that is until you have a desire for a real mans cock in your anus instead of sex toys. Just enjoy it, sexuality is just a label, men have a prostate and that produces sexual arousal - it's natural.

Relax and enjoy yourself, perhaps even tell your GF about your enjoyment or anal sex toys, even involve her, let her use your toys on you or buy a pegging strapon, it may help clear things up in your own head if you are really having issues facing your fears of being bi or gay.