I can't find happiness because of Ex

I started suffering depression when I was pregnant with my son. It's only seem to have gotten worse. I have a great life with loving friends and family that support me and care for me. But It's like I won't allow myself to be happy. I feel so ungrateful and selfish that their doing everything to make me happy and I just can't be. I'm miserable all day, now I've take to acting happy so I won't worry them anymore But when I'm alone all I do is cry. The only negative thing that has happened is that my sons dad cheated and left me while I was pregnant now that woman is pregnant and their engaged. He was terrible to me and I should be so happy He's gone But instead I miss him and allowed him to continue using me for sex and leading me on. I finally decided to tell him enough is enough. He verbally abused me again and cut me and my son off for good and says he wants nothing to do with us. He constantly tells me him and his soon to be wife are going to have the family I wanted and my son is only going to get child support. And instead of appreciating everything that's good in my life I constantly focus on the negative and miss that no good man. I feel terrible about myself for not being able to give my friends and family the love back that they give me I can't even connect with my son. I just don't know What to do anymore, I've been on anti depressants for a year and It's just not helping. I don't understand what's wrong with me. I just want to be happy again.

Never blame your emotions on someone else. Only you can control how you respond.

He is not a nice man, but he is no longer your problem. KK-work on making yourself whole .