Child support

Hi. Not sure if this is the right channel to rant. But I am a single mum to a 14 month old boy. His dad and I actually dated for a measurable amount of time ( ~ 4 years )and it wasn’t a one night stand kind of thing. The thing is. When he didn’t want to settle down together I did a lot of horrible stuff. Such as spam calling him and tracking him down. He is paying for child support as we previously had an agreement signed. But recently I realized the girl whom forcefully got between us, is actually together with him now. What should I do? He is no longer in contact with me. All he does is to drop me a message monthly that he have already wired the money into our child’s bank account. He negotiated saying that if I were to drop this monthly alimony, he will hate me less and won’t ignore me. But how can I trust him? I am currently working now, but I don’t feel right letting him scoot free just like that, that’s why we signed the agreement initially. I have talked to his parents but they chose to ignore me. Deep down, I just want to have a complete family for my son. I haven’t had a complete family growing up and really wished my boy would have it. Is there anyone that we can go to in order to mediate the strained relationship between us? Is it really no use anymore? :-( I don’t really want to give up. I know I should move on seeing him that he have already moved on. But I really feel so indignant that he didn’t even try to give our family a chance. Or as horrible as it sounds, is there anywhere I can flame this girl publicly? She’s working in a reputable firm and holds a pretty high position. And if you’re wondering if we are teens no. We are all in our 30s.