Relationship advice

Hello, I’m a 21F and I’m currently in a relationship with my girlfriend. We’ve been together for 1 yr+ and we are so deep in love even tho we are past the “honeymoon” phase. I’m writing on here because I have no one else to ask. We are happy and have great communication etc. However, its easy for me to get turned on by her but I’ve never been able to orgasm when we have sex. She does orgasm and I know she does but idk what’s wrong with me. And recently I’ve been wanting sex from a guy. Just to feel the domination from a male and the penetration is what I fantasize. Not that I would ever cheat but I don’t know what to do. I don’t want to break up. And I want to orgasm together. Help!