Sexual relationship with best friend

So I’ve been friends with my best friend since 2015. We met in Australia and became close over a short period of time. I have since moved back to my home town (in a different country) and we still keep in regular contact. He and I never had anything more than platonic friendship. When I lived in Australia it was brought to my attention that he had fallen in love with me. I was the first girl he was attracted to that actually stuck around to be his friend after he had attempted to ask them out and was rejected (he is autistic so he forms very strong attachments to people and cannot handle change well). Before I moved back home he had told me that he was no longer in love with me and that we could finally just be friends without his feelings for me and my lack of romantic feelings for him getting in the way. I was ecstatic. Our friendship had the room to blossom into a really wonderful close friendship, like it had been before, but even closer - which surprised me, because it was now long distance. Fast forward 2 years, he tells me he’s been increasingly lonely. He lives rurally and has a difficult time making friends and so I introduce him to a friend of mine who has lots of spare time and would be able to keep him company on Skype when he’s feeling lonely and needs friendship when I am busy working or studying. Sometime throughout this online friendship with my other friend, they begin a sexual relationship, he also confesses to her through this sexual relationship that he is still in love with me. She tells me and I confront him about it. He denies it at first and says he was just confused, but after leaving the situation to calm for a few days, he then confesses to me that he is in fact in love with me and through that, confesses his sexual relationship with my friend and that for so long he was trying to stop his feelings from coming out because he was scared it would ruin our friendship, but after this sexual encounter with a practical stranger (my friend), he trusted her enough to tell her how he was feeling and she convinced him to be honest with me. This is where things began changing for us again. I think this was the first time I realised he could be sexual, he was so innocent to me for so so long. My friend would send me screenshots of their sexts and it changed my view of him. If we once again fast forward a couple weeks or so, he and I develop a sexual relationship. Obviously because we live in different countries, it was only online. Sexting. Not to mention he was and is still a virgin. His experience is literally one hand job and a BJ in the back car park of a nightclub. My experience is a quite a bit more than that. My other friend began trying to convince him to sext me, I didn’t ask her to but she thought it would work and she knew I didn’t have the confidence anymore to go out and hook up with guys... plus I think I got lonely. I was sexually assaulted in Australia and I redeveloped a really toxic relationship with my body and with sex. When I arrived back in NZ, I felt as if no one could ever be attracted to me or want to have sex with me and so I think I got really insecure and lonely and after awhile I realised the only person who wouldn’t judge me sexually (because he’s so sweet and kind, but also because he’s autistic and quite naive) was the guy I’d been friends with for years. I don’t know why we still do it, but that’s essentially the advice I’m seeking. After we sext I feel literally revolting. I hate myself. I hate him. I hate sex. I hate my body and I never want to do it again. Then the next day I will feel quite the opposite and want him rather badly. I also get jealous when he is talking to other girls and when he tells me he’s been on tinder. I just want to know what people could think all of this means. Is it because I’m repulsed by myself? Or repulsed by him? Is it because he’s a virgin and I find the lack of experience unattractive? Why do I feel like sometimes I swear he’s the only person who could ever satisfy me, the next day I’m repulsed by him and the next day I feel as if I could be in love with him? And if it’s the last one, what holds me back? Why do I not want to be with him, yet I feel anxious and horrible if he’s interested in anyone else? Please help. I have no idea what to do. I don’t want this to mess him up just because we want to have fun. I want to still be best friends and I want to be able to have a good friendship beyond the sexting. I find it hard to face him and talk to him a lot of the time because the sexting is such a prevalent part of our friendship now. I don’t know why it makes me this insecure

You have answered your own question. If it makes you feel bad afterwards, you shouldn't be doing it.