FWB breakup

I had a thing with this friend and it had lasted for about five months. It ended three weeks ago because he has a girlfriend now. At first I was not okay with it, mostly because it happened so fast - we slept together and few days later he said he is in a relationship with her. Now I am kind of okay with it, still not 100% over him, but I see I'm going there and actually looking forward to getting over him and discovering new things about myself (like every breakup did to me).

I want to stay friends with him, but it is (still) difficult for me to separate our sexual life and friendship. It hurt me because I wasn't his first choice even tho we had such a great relationship... it is true that I didn't want it to be ''real'' relationship and I had my reasons (I still stand by them), but every time we talked about it he said the same so this came pretty unexpectable, fast and painful. Also, his girl knows about us, but she doesn't know when it was happening.

I know it is fresh and I know it will be alright. I hope we will maintain our relationship/friendship in this new dimension. I'm totally great on my rational level, but my emotions still have to make a shift. My only problem while shifting my emotions is staying sane and not getting down the spiral of overthinking and comparing myself to her.

If you have any advice or similar story, feel free to write in this thread :))