Should I tell her he's cheating?

I’m a little conflicted. Basically, I knew a guy for around two years, we started sleeping together for about 6 months casually, found out that he in fact had a long term girlfriend. Broke up with that girlfriend and got a new one and we parted ways, two months later he gets back in contact with me asking to hook up. Told him I had a partner, but we could be friends. Found out he has a POF profile (received an email, went online to delete it and saw he looked at my profile) it’s obviously him asking for hook ups, casual sexting.
What should I do? Part of me think I should leave it, but it also annoys me that he’s cheating on yet another girl and will be stringing another girl along like he did with me (having me think he was single)

I know his new gf wouldn’t be happy with the pof profile (not like he’s in an open relationship) as he made it clear when he got back in touch with me it would have to be on the sly. Do I tell her, if I did I would block her on fb and then message her as my name wouldn’t come up, I have the evidence of the POf account and the details of his snapchat? Part of me just thinks I should leave it and not get involved, I’ve deleted him on all social media, and don’t want to be friends with him anymore but also don’t want to come across as bitter and sly if he did find out it was me. Just makes me feel so uneasy, if someone knew my bf was cheating, or attempting to cheat and didn’t tell me I’d be so upset. Thoughts?

Guy is/planning to cheat on gf

Told her and she doesn't believe me, glad I did it but he's obviously denying it as shes like 'my bf has told me about you' and doesn't believe me. Oh well, told the truth now she can decided what to do with it and I don't have to worry about it anymore

I’m a little conflicted. Basically, I knew a guy for around two years, we started sleeping together for about 6 months casually, found out that he in fact had a long term girlfriend. Broke up with that girlfriend and got a new one and we parted ways, two months later he gets back in contact with me asking to hook up. Told him I had a partner, but we could be friends. Found out he has a POF profile (received an email, went online to delete it and saw he looked at my profile) it’s obviously him asking for hook ups, casual sexting.
What should I do? Part of me think I should leave it, but it also annoys me that he’s cheating on yet another girl and will be stringing another girl along like he did with me (having me think he was single)

I know his new gf wouldn’t be happy with the pof profile (not like he’s in an open relationship) as he made it clear when he got back in touch with me it would have to be on the sly. Do I tell her, if I did I would block her on fb and then message her as my name wouldn’t come up, I have the evidence of the POf account and the details of his snapchat? Part of me just thinks I should leave it and not get involved, I’ve deleted him on all social media, and don’t want to be friends with him anymore but also don’t want to come across as bitter and sly if he did find out it was me. Just makes me feel so uneasy, if someone knew my bf was cheating, or attempting to cheat and didn’t tell me I’d be so upset. Thoughts?

Guy is/planning to cheat on gf

Told her and she doesn't believe me, glad I did it but he's obviously denying it as shes like 'my bf has told me about you' and doesn't believe me. Oh well, told the truth now she can decided what to do with it and I don't have to worry about it anymore