Okay, this is a rather odd story so I'll try to explain it the best as I can.
Around 6 months ago, I became friends with this guy, he was decent company and kept me entertained. Within weeks he developed a crush on me, so I decided to give him a bone and we started having sex, pity sex, because I do care about him and felt bad through all the things he's constantly put through. Now there's nothing really attractive about this guy, he's autistic, a little overweight, ugly, living on welfare, constantly depressed, poor, annoying, a 5 inch penis and has so many problems it makes the Jackson 5 look like a happy family. Overall a 3/10.
Now the thing is, I told him from the start I didn't feel the same way and it was just friends with benefits. He tried his hardest to please me, and so he started doing every little fetish and kink I have, so sex with him went from boring to freaking amazing. Basically I molded him into the perfect f*** for me, and simply thinking about him is enough to get me aroused. He did everything I wanted sexually, and I loved it.
2 months ago I started dating my best friend, we've known each other for over a decade. Now my bf is great company, smart, finishing programming, good looking and overall an amazing person. He tries his best to make me happy, buys me lots of stuff even tho I keep telling him to stop wasting money on me, always makes me laugh and treats me like a princess. I am very in love with him even tho I most of the time get a little bit distant unintentionally (I have ADHD), yet he completely understands that and doesn't mind.
Now when it comes to sex, he is kinda lacking. It feels like the only thing doing it for me is the fact I love him, but to be honest, it's boring. He is very slowly picking up on a few of the many kinks I have, but it doesn't feel like it'll be getting much better.
Now me and my 6 months friend are still in touch, I talk to him weekly and we hang out, he's still my friend. Problem is, he keeps suggesting we go back to doing it, and even tho my heart wants him to stop, my legs doesn't. Everytime he suggests it, it just feels like I'm gonna jump on him and have sex right there and then. He turns me on so much it's not even funny, but I don't wanna cheat on my boyfriend. I hate cheaters and don't give them second chances, nor have I ever cheated or ever will, even if it kills me. I don't wanna cut contacts with said friend either because he's been through a lot and honestly if I do, he'll most likely kill himself as he has no other friend and relies on me heavily.
TL;DR Don't wanna cheat on my boyfriend but friend turns me on too much. Please help, what do I do