Bottom only here. It's a bit weird because I'm bi and my longest lasting relationship was with a woman, but ever since I can remember starting thinking about sex the idea of penetrating with my penis made me very uncomfortable, a feeling that became even stronger when I started having sex with women. It's not that it was entirley unpleasent, I liked the feeling of cumming (but not even that much), I don't like what comes before, it give me some sort of sexual disphoria (I don't know if it's an actual thing - but that's what it describes it the best). When I realized I liked guys as well I thought that maybe that was the reason, that it'd be different with guys, but no, I tried it and it was the same. I actually was a bit depressed about it because at the time I rejected entirley the possibility of bottoming because it seemed too gay and too painfull, so I thought I would be never sexually satisfied. But eventually I started fantasizing about it, and the more I thought about it, the idea of being the receiver, being in the passive position became appealing to me, and more suited and natural for me. I started practicing, first by myself with toys and other object, then with guys and... well, ever since I broke up with my gf I'd sex mostly with men and only as a bottom - and I can say that I'm fully satisfied