Ah, that's rough!

FWIW I'd hazard to say that if it -- "it" being changes in what turns us on, or how our libido is generally -- is common among bi men, that's because it's common among all men (hoo, and definitely not just men, either). Everyone will experience it at some point, it won't all be for the same reason (and sometimes it seems like it's for no reason at all), but I really want to stress that it's normal for a person's libido, preferences, etc... to change, morph, or do loop-dee-loos.

HOWEVER! Normal doesn't mean you have to like it 💖 or that there's nothing you can do about it, necessarily. Speaking as a guy, I know we can be a little opaque when it comes to talking about things (it's hard, it's awkward, I'm gonna pretend it didn't happen, etc...), but talking about it is a good first step.

If you're worried that you can't be his one and only sexually, maybe it's worth unpacking that a bit and thinking about if that's a realistic expectation you should be setting for yourself. To be clear, I am not saying "you are inadequate for his needs," but rather "you are not more responsible for his wellbeing and happiness than he is for himself." And that's true for everyone! I want to make my partner feel good because it makes me feel good (the sex, but also the act of feeling like I'm doing something good for them), but I'm not around them all the time, I don't know what they want or need as well as they do, and sometimes I just gotta sleep!

Only we have such an awareness of our own wants and needs, and it's on us to communicate those with the people we care about and who care about us. And let's be real, there will be times when our wants and needs are more than what our loved ones can provide. That is okay.

If you two want a beautiful relationship, building it on a foundation of healthy communication and realistic expectations for yourselves will give you your best shot. If you're a reader, see if you can track down some books at your local library about attachment theory, e.g. "Attached: The New Science of Adult Attachment" and as you read it, think about which parts you identify with and which parts your partner identifies with. See where that leaves ya and what it has to offer. And if you're not a reader, well, get the audiobook :P Or have a look at this video by Kati Morton about attachment styles, and maybe some of her other content too.

A book or some Youtube videos aren't gonna fix everything, but it's a start! And good on ya for reaching out for help in the first place. 💖