Should i??

Ok so i have a serious question for all you ladies. So my ex and i are separated but technically still married. He has started dating a girl and they have only been together for a month and they are already living together. We have a son together who has adhd.. i don’t really want my son to meet her until they have been together longer bcuz he is known to date girls only for a little bit lately since us. I am not keeping his son from him but i ask that he not bring her around right now. He doesn’t do a whole lot for his son as it is. No child support or anything like that. Do you think i should let him bring his new gf around our son already. I’m just so tired mentally and physically and would like to date myself but it’s hard to find someone i trust to watch my son... does this make me a bad person... please help thank you!!