I have the same story, mostly, except that she loves the fantasy I tell her about like that while we're having sex, but she is staunchly against ever trying it. She also would never allow it. I'm criticized constantly for having sucked dicks in the past. As with you, absolutely no romantic interest in guys. I just love dicks, soft and hard, and balls as much as I love tits and pussies.
If we ever end our relationship, I will likely never have another exclusive relationship. Should that ever happen, I will not hide that I am a flexi-sexual. I don't think it is at all uncommon. I think its just one of the most unspoken interests and hidden by most who won't even admit to themselves, even though they secretly feel it.
I would want people to know that I can have interest in play that does not require romantically emotional attachment and that a relationship of emotional attachment is not conditional upon sexual enjoyment. I would not ever have romantic feelings for guys. That is reserved for women only. However, if I ever do have another relationship with any other woman, she will know of my interest in and desire to play with dicks and balls, and she will have to accept that. Not being accepted in every way is not a good way for a relationship to work.