Don't know if he's the one anymore

So I've been dating this amazing guy for a while now but recently I started talking to this guy that I used to have feelings for and used to be really good friends with but drama happened and we didn't talk for two years .. Now we are talking again and there is a little bit of flirting going on between us and I don't know if it's just old feelings coming back or what but I think I might be into him. I'm still in a relationship with the other guy. We've been fighting alot lately and he said I've changed.. I think this is because I've been talking to my old friend again and developing feelings for him and ignoring my current boyfriend.. I feel like such a shit person right now because I know if my boyfriend knew he wouldn't be happy but I don't want to stop talking to the other guy.. And I don't know what to do.. Because I think I like him but I still do love my current boyfriend as well and I really don't want to hurt him he's such a sweetheart.. The guy knows I have a boyfriend but I know he wants to be with me. I care about them both a lot. Should I tell my boyfriend and risk our relationship or cut all ties with my old friend again?