Dear Sandy, I totally understand what you are saying. My jaw dropped when I was reading your story because I am in quite a similar situation. My boyfriend wants a lot less sex than me and often rejects me in bed. He doesn't want to sleep with other people, but I have developed strong desires for others and therefore we are thinking about becoming polyamorous.
I don't have a solution right now for you, as I am also struggling in this new field that my boyfriend and I are exploring. But I suggest talking to your boyfriend and finding a way to make sex less pressuring for him and yourself. I am trying to find ways for this as well, so I would like to hear what other people have to say. I can understand your feelings of jealousy, it would be interesting to talk to him about it openly and show your vulnerability.