Help ! Need advice ! Am I crazy?!

Okay I have no idea where I should put this but oh well anyway so this is going to be long so sorry in advance but I here is some back story :

3 years ago I was in a very serious relationship with this guy and it ended very badly but we had been together for a very long time. In that time he had given me a STD and towards the end I was treated very badly and definitely mentally abused by him. The break up was very traumatic for me at the time.

Well now .... I am now in a relationship with my boyfriend and last year around this time my boyfriends cousin started dating my ex boyfriend and I let her know that he wasn’t a good guy and all of this but she did not listen. I made a big deal about the entire thing and how I would not be around him but just got told to suck it up by my boyfriends family. I ended up having to spend Christmas with him sitting across the table :/ . They ended up breaking up a little while later thank god . Well now I am 24 weeks pregnant with the same guy I was with a year ago and I just saw on Facebook that my boyfriends cousin is back with my ex AGAIN. I am yet again not knowing how to react. I do not have any romantic feelings for him anymore when I am around or in the presence of him all I want to do is scream because it’s not fair that I have to sit and be around him. I do not think I will be able to do this again like I did so calmly last year. My boyfriend tells me that I have no right to keep his future son away from his family no matter if my ex is there or not. I try to explain to him that I feel betrayed by his family not sticking up for me but he says I should just be able to sit there and coexist because he is just my ex. Will someone please tell me if I am being crazy and should just suck it up or if they are being completely unfair to me and I should stick my ground. Oh and my mother and my side of the family tells me every day that it is not fair to me and that I shouldn’t have to go through this just so they can have play perfect family... so that definitely feeds the fuel to my upset fire. Please give advice I feel crazy right now !