So against pegging, help!?

Greetings.. This is a very uncomfortable subject for me and I can't seem to be happy with the results I find online. I suppose I'm looking more so for a coping/acceptance thought process and how to start not shunning this kink.

*Go to ------- for the direct question..

My boyfriend and I have been dating for 2 year now and have been living together almost a year now under other people's roofs. (Fast I know, considering he's my first) Aside from this issue we both have more issues (anger, depression, anxiety, etc) but one thing at a time.. Recently this has been bothering me as it's something I believe will determine how much longer this relationship lasts for me..
Don't get me wrong I LOVE him, but sex to him is a higher priority than me. ( I considered myself asexual before him, I still kind of do, though he's convinced me I'm not)
Anyway, I am really good at reading people and when I met him I had a feeling he was either bi or gay and this was going to be a cover up relationship. I liked him and he denied all things of the sort. (His family and friends thought the same thing of him) So I went on with the relationship, always having that thought in the back of my head but it didn't ruin anything or make anything less of us or him; I really didn't care. What I do now care about is the sexual part, because it now involves me..
He's a weird character as he always goes on about "What if.." scenarios and I hated them, now I go along with them to shut him up. Things from "What if god and Lucifer were an item?" which would become a little story after that thought all the way to "What if I lost my genital and I only could be pegged?" In the beginning of our relationship it caused a major problem because one that really got to me was "What if you found another girl underwear here?" and sorts of the lines of cheating. And those things led to a disaster as I suffer BPD and hurt him before he could hurt me.
About a year and a half in after I moved in he did a random confession of how when he got his first job he went out and bought lingerie and tried it on just to see "how it feels" and then said he threw it away. Later on the whole "what if" game got worse and more sexual ideas came flowing from his mouth. One time he had a very vivid and lively way of a position if we were to have a threesome as with another girl. I was disgusted. I wanted to throw up... I'm not homophobic.. I'm just a prude who is slightly vanilla. A relationship contains two and only two..
So the other night we were on the phone and another "what if" popped up and it was about if he had got his genitalia shot off and the only way he could be please at that point was by pegging and if I do that for him. My response was no and he went on to saw how depressed that would make him not having his junk any more. That eventually he'd kill himself and how I'd feel not having sex anymore. I said you could still please me. And he said what about me.. Told him that's a selfish thought. But I'd be okay. (asexual mind) I could care less. He again set it up is what if we wouldn't do bdsm in trade of pegging, to be fair. I told them those are total opposite and aren't interchangeable. BDSM to me is the mindset... Pegging is an action. I want a dominant in my life and a man who is getting pegged isn't what I consider that.. This my main issue with it. In MY mind and I can't rid it is that pegging is an action of submission.. To be it degrades a man. Of course there is other sides to this, but this is my perception... So no I want nothing with this thought or idea. I want a total Dom and not the slightest of fem intentions.
How do I get over it?

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Dan is 24 and I am 19. First loves living together for 2 years now. I believe he's trying to come out? Or is he just trying to tell me he wants to be pegged?

Timeline:

-His confession of loving My Little Pony. Family already believes he's gay/bi, I thought that the first weeks of hanging out. He denies it. So he is not.

-Became more open of our fetishes. Only thing he said was anal, nothing else.

-A year together, at this point living together, confesses that when he got his first job he bought lingerie, tried it on to "see how it feels" then he said he threw it away..

-Complains about hemorrhoids. Long bathroom breaks. Deleted history on phone. Some times he shaves his behind. (May be reading to much into this one, but we have a really good diet and I only every had a hemorrhoid once and that's when we tried anal once..)

-Continual "what if's" of pegging. If I'd do it, if my finger slipped it, if I were to how often, would I leave him if that's what he really wanted, etc

-Yesterday, with a heavy sigh "I rather be a girl than a boy" after a very vulgar "what if" setup of "What if I lost my genital and I only could be pegged?". My response, I dissociated and said I'd have some other girl do it as I left him to do his business. He insisted he'd want me to do it. He then said if it was role reversal that if I were to withhold my fetish against me (BDSM) if I were not to that. I argued it was nearly not the same and unfair. Basically he was trying to find a loop hole in were I said yes to this "what if" case. (Over phone call)

-Had intercourse this morning and I was totally detached swarmed and engulfed with the disgusting activity of his make believe wishes and then turned grumpy and still detached through out the rest of the day.

I don't care if he's gay, I rather that than in engage in the pegging activity. I don't think I could go on with a relationship where that's his desire, but I don't want to be as shallow as that... Is there anyway to cope with the idea that this could what he subconsciously wants?