I'm having ptsd or some kind of trauma episode.. I dont know if anyone has advice or can relate?

5 yrs ago I got married and got pregnant right away. I gave birth in nov that year and when my son was 4 months old my husband cheated on me.. It was horrible.. I stayed with him for 1 1/2 yrs after that but I finally had enough of the lies and emotional abuse so I divorced him. Shortly after that I met my boyfriend and we have been together for 2 yrs. I just had our baby almost 4 months ago and today I'm crying/ anxious about the past.. I keep thinking that my 2nd child is at the age that my 1st was when my ex husband cheated on me... I trust my boyfriend but I just have this overwhelming fear cuz of what I had went through. Doesnt help that we haven't even had sex since before our son was born (is that normal? He didn't want sex when I was pregnant either cuz there's a baby in me so he was weirded out. We did have sex a few times when I was pregnant but not much. Baby has been clingy to me so thats pretty much why we haven't yet but he doesnt act like he even wants it or misses sex with me.. I was begging when I was pregnant. Before I was pregnant he was fine).. and I've been so emotionally drained/ depressed for a while. Ive told my bf how drained/depressed I am and he doesnt get it and acts like its nothing. He complains when i ask him to hold our son for me when I need to poop or just do chores or whatever.. i think its cuz he cries a lot when he holds him. we have argued about it a lot.. anyway, thats a whole other story.. I feel like with the circumstances he'd be in more of a position to want to leave me or cheat than my ex husband. I know they are 2 different men and my boyfriend wouldn't do that. I've told him about these feelings before our son was even born and he tells me he wouldn't do that and understands why I'm worried. I was just crying, thinking about the past and the present.. and I just think I'm going through some kind of trauma from my past. I never fully healed from it.. I also don't really trust going to a counselor cuz I went to one with my ex after he cheated and she would say things that would help him but I never got anything out from it.. maybe I need to really talk things out with him or just see a different counselor. Idk..