Confused (25F)

I’ve dated men all my life but have always considered myself bisexual. I’m sexually attracted to men and when I start a relationship with men it’s usually great and sex is there but as time goes on I always go back to looking at women and “getting off” with visuals of just women. Sex usually becomes an issue in past heterosexual relationships because my sex drive decreases toward them. I’m still visually attracted to them but the sex just isn’t fulfilling. I’m worried that I’m just fantasizing about women because I’ve never had sex with a woman before so I’m idealizing what it would be like. I’m just so confused and need to figure it out sooner than later. Please help.