FWB got GF

So I’m just upset I guess. I’ll give you some background.

My ex and I have been FWB for around 2 years now, we wouldn’t have full on sex but foreplay and other stuff u no. We were really close, like he was pretty much my best friend but he very recently got a gf. I know I should just move on but it really hurt me I suppose. I don’t have strong feelings for him coz he asked me out but I did say no and so in a way it’s my own fault but i just don’t know what to do. Obviously we won’t be FWB anymore and he still wants to be friends but I just don’t think I can do it