Can't quit my FWB!

I've known my FWB for almost 3 years now. we were friends first for the 1st year (he had a gf) and it wasn't until he broke up with her around the middle of year two that we started getting spicy. 🌶 so now we are at this weird place where we've never had sex or done anything intimate in person (our entire fwb relationship has been conducted via phone) and we just sext back and forth but with random friendship conversations in between. the problem is I know I need to get rid of him and I have tried. he talks to me and asks my opinion on other women for crying out loud, if that isn't a red flag idk what is. we are just comfortable with each other. the farthest I've gone is to block him for months at a time but he always comes back. I think it's because I'm his constant and we've been friends for so long. but i know deep down he us just using me and will drop me the minute he decides he wants a real relationship. i just can't imagine losing his friendship because outside of just sex, we have a LOT in common and we talk every single day. its just so hard to keep this going knowing whats going to happen in the end.