Umm, not sure, but I think Sofure Buka may have some stuff you'll be looking for:
http://www.mangago.zone/read-manga/sofure_buka/
Another would be Never Understand where this girl has a crush on the seme and actually (spoiler) has her "boyfriend" try to rape the uke while she video tapes it.
If you haven't read Sign yet, then you're in for a treat. (Spoiler) he's not an ex, but he tries to harm the uke to get revenge on the seme. Not gonna go.in depth about it since I'm not sure if you read it.
Thst is about all I could think of
( ̄∇ ̄")
They might not meet the "psycho ex" criteria you're probably looking for, but I thought it would be something similar to that.
I’m not sure but Dark heaven has an obsessive ex-girlfriend that’s attempts to kill the uke. http://www.mangago.zone/read-manga/dark_heaven/
Can you guys recommend me some yaoi's where the seme's ex girlfriend is very obsesive and bullies the uke and or tries to kill him. Also is there any yaoi's that the seme's ex girlfriend is still really obsessive and finds out that he is with a guy and gets mad and tries to convinse him that he's not gay and should go back to her but he wont. Or she could find out he is dating a guy and spread rumors about them to try to get them to break up or something. I really thank you so much if you would reccomend me something exactly or similar to what i described. Thank you so much!