I know I shouldn't do it

Annette
So me and my ex broke up a while ago. Everything was going good, then he said he wasn't ready for a relationship. We tried being friends with benefits but it just wasn't working. So we tried being just friends (more like I tried to keep it as just friends, he was still trying to get benefits). So one day he's telling me that he needs me, that he craves me. Then 2 hours later he tells me he met someone. This was all through the facebook messages app so I still have the messages. We had a big fight and I told him I was done and blocked him from contacting me. We met on Plenty of Fish so he would keep looking at profile even though I blocked him from messaging me. Like an idiot I unblocked him. Needless to say we had another fight, so I blocked him again. He was jealous that I had been talking to other guys and basically tried to make it sound like I was going out with every guy I came into contact with. The truth was I had only been on one date from when we broke up until our last fight, but he didn't believe me. And even after I blocked him again he still kept looking at my profile almost on a daily basis. He was even updating his pictures. Then one day I noticed his profile was gone from the list of those who had viewed me. So I did a username search. It was still there just hidden. Because we had messaged each other in the past, I could still access it. But the city had also changed. I took as he lost his job and was moving. He's not originally from the town we're both living in. A couple of days later I decide to check his facebook page to see if he had moved already, but it still had him at the same job, so I don't know if he's staying or going. But under his friends, I saw the new girlfriend. I know it was her because her profile pic is of the two of them and I looked at the comments. I wanted to tell her she was with someone who's shady because of what he asked me to do to him before telling me he met her. I even wanted to send her screenshots of the messages. But I know that makes me look like a psycho ex that's trying to get him back. Part of me does still want him and part of me wants to get even with him for how he treated me. Plus part of me wants to genuinely warn her before he does the same thing to her. I'm just started seeing someone new but I know he's not the one, just the one right now. I feel like I've been talking myself off the ledge since I discovered who she was. I'm doing the right thing but not saying anything to her, right?????