TIFU I’m dating someone i’m not supposed to.

I’m actually not dating him, but he’s my sneaky link.
Okay, so, i have a boyfriend currently and we’re together for less than month. We met on our mutuals friends birthday. It was a birthday of boyfriend ( his friend) and a girlfriend (my friend). We started dating a little bit after that. Eventually our friends have broken up. I sometimes hang out with my bf and his friends, including my friend’s ex. We hit it off, i realized that he’s interested in me. We are literally the same person.
He called one night, out of nowhere, saying stuff and that he’s hurt cause of the breakup. He asked me can i see him. I went out, we talked. He didnt seem upset at all. We hung out for 4 hours at the bench, and at one moment he looked deep into my eyes. After that he kissed me, very hard. He said he has been waiting for this for a year (they were together for less than a year).

We did talk about my bf during the hang out, he said he’s so happy for him and that my bf is very much in love with me. He didn’t seem like he’d lean in and kiss me afterwards.

The thing is, we cant do this. I cant see him, i cant talk to him. We live in a small city. He excises me more than my boyfriend. Idk if its the feeling from doing something im not supposed to, or if i like him in general.
Even if i know that one single mistake will ruin my morality, my friendship, relationship and everything, im still seeing him. I cant stay away from him. He talks to me about everything, i always ask him about his feelings from his breakup. He told me that he wishes he wasn’t so interested in me because he likes me as a friend, but apparently he cant stop touching me and kissing me anytime i sneak out to see him.

We’ve hung out with my bf and their friends after that, we werent weird, everyone was just shocked how we clicked very fast.

Also, I knew him before, obviously because of my friend, but we talked before, had discussions about politics and history, and he was always telling me even in front of her how smart i am, how he can only have these deep talks with me etc, but i never thought he actually likes me like that.

Also, i never imagined myself as a cheater. Guilt is eating me out alive, i asked my sneaky link what should i say to my bf, he told me to think about it later. And honestly, i cant just say hi im cheating on you with your close friend, that HAS to stay secret cause i dont want to loose my friend… and ik i cant think about that rn because it looks like im doing everything to ruin my friendship.

I like the adrenaline, i like my SL, hes so passionate about me… i know that there are no heavy nor deep feelings, but im okay with that (as in a way that he’s using me). Im agreeing to that. But i dont know how to break up, how to say anything to my friend. I dont plan on dating my SL its just so different than my previous romantic situations. What the fuck should i do.

Also he broke up with her two weeks ago, and im dating my bf for 3 weeks rn.

TL;DR: my friend and her bf broke up, im dating his friend but we’re seeing each other. He said he’s been in love with me for the last year.