Am I a bad person for wanting sex with someone I shouldn’t?

(Putting this in r/sex due to the nature being purely confusion around my physical/sexual partner choices)

Last year a friend broke up with his girlfriend and they both always call me, and IMO we can all talk to who we want to talk to so no problems there, I just ask them to leave me out the mess. Recently they have been extremely bad to the point he has gone to see another girl, she has said she wants nothing to do with him which is all well and good. She has come to me a lot recently and it’s been completely fine with no issues… Until last night.

I’m broken myself and I’ve just come out of a few years of a toxic relationship and for over 8 months now I have had NO intention of seeing or talking to anyone with intimacy, sexually or romantically. But last night things took a slight turn…

It started with the usual, she phoned me and was just upset so we were talking… Ended up being a three-and-a-half-hour phone call and the last hour and a half were us just talking about sex with each other… I had full control of it and we both agreed it was so wrong… But it just felt so right at that moment for both of us. I’ve never thought of her like that, I’d never go for my friend’s exes as I’m not that person and I kept telling myself that. But something came over me last night, I liked every word she said and she had the right attitude and talk for me, I also liked the fact we weren’t supposed to be doing/talking how we were…

I physically can’t help how I feel though, right? Even knowing it’s wrong, I can’t just ‘change’ my feelings? I have said logically nothing would happen right now and it can’t because of my friend. I’ve NEVER wanted a friend’s ex and this is the first time so I’m clueless if I’ve changed myself recently or if I’m just lonely or if it’s because I don’t look at him like a friend anymore?