So i have a few comments on this. 1. Im bisexual 2. I was born female, but i identify as non-binary/genderqueer now. 3. Im currently dating a cis male. 4. I have rape fantasies from both perspectives too. And yes, i also feel messed up for being into that. Sometimes even guilty. I don't want that to actually happen to me or other people. I would rather role play it if i can. Basically to just pretend there isnt consent to get the rocks going. But of course, safe words, communication and the whole shabang. (Full disclosure, i havent been able to admit to any of my significant others about this fetish of mine, i choose to communicate it in different ways)
So ill leave gender comment for last, but heres my perspective of what could be happening or for me what my experience was.
I get off at being forced and forcing someone else. Its more about getting lost in the pleasure, mind break for me. I want to just lose my mind. My ex gf was also into this somewhat, and it was really fun to get her all weak and quivering from this kind of play. We were into BDSM sub and dom play with lots of degrading dirty talk. We would do alot of after care to make sure everything was alright and we communicated. This might be a good outlet to start with when communicating these desires to youre boyfriend.
Now.. In relation to imagining raping him or maybe just from his perspective, if could be that you are also just getting off at the idea of someone getting off at your intense pleasure (from your kink). Im like that as well, i want to hear and see that someone if getting off at me or i usually cant get off. You need to try and understand which is which. What do you want to try out and what is just fantasy? Do you want to try a strap on and butt stuff? Do you want to tye him up and ride him? Gag and blindfold? Figure out what props, actions, and dirty talk you need and find a realistic way to implement that into your play. Of course he would have to be olay with it. But it seems the first goal is to get him to be more aggressive in his dom play with you. So defiantly talk to him about things he should say or do. Maybe practice challenging you. Make him aware of what you want. Also dont let him shame you either. It could be that you want to see your boyfriend squirm the same way i did from my ex gf. I havent been a dom since her. My current partner isnt into butt stuff and he prefers to not be tied up. Also he prefers to be dom and i let him usually. And im not ganna force it. And to be honest, i hadnt thought of any rape fantasy of me forcing a guy until i met him. Idk hes just so... Cute xD. We are getting more aggressive now and more degrading dirty talk. Im a really big switch XD.
Now onto the gender. I didn't questioning this until around 20 and only realized around around 24. The reason i mention this is because i also have almost the same fantasies as you've described. It maybe that you get off at the male perspective because you're fluid or NB. Maybe your egg is cracking (if you're questioning i recommend r/egg_irl to see if you identify with any of it at all) Also if you are NB, that doesn't mean you're not straight because straight just means you like an opposite gender than you. It also doesn't mame your bf not straight for liking you either. This experience from my kink wasn't the only reason i questioned my gender, so i don't know what your story is, but im just throwing it out there because i understand what you're saying in this post. Maybe i have my reasons and they're different than yours but i wanted to just cover all the bases through my own experiences. Maybe youll learn something about yourself. Or maybe its not you, just wanted to make sure.
I hope this helped you in some way. Just talk to your bf about more kink play and then at some point bring up the rape fantasy once you've had more practice in the kind of scenarios you want to do. Again i haven't told my current partner the rape fantasy yet. We're still building to that kind of play. Ill have to see if he's down with it anyway. But good luck! Ask me any questions you want of you need it.