Do you believe its right to be jealous of your partners past?

Im thinking about ending a relationship i’m in. We have been together for almost 2 years and our relationship has been 50/50 in the terms of beautiful and rocky. My partner has dug into my phone and went back into old messages from 4+ years ago (messages I didn't even know I still had), WAY before him and I started hanging out and dating. (Keep in mind, I was single for 2 years before dating him and did casually date and explore my sexuality but not crazy in my opinion! My body count is 4 including my 2 past relationships, had 2 one night stands during my single period & i’m 26). He uses my past against me, and shames me for it by calling me degrading names whenever we get into a heated argument (slut, whore, stupid bitch, “yeah you wanna fxxk other dudes but not me” etc) He basically brings this up as if its relevant to our relationship and as if its happening today. I have no contact with these people from my past. They all live in another state. Theyre not even brought up or talked about by anyone but my partner.

Every day I remind him I love him and I only want him.
whenever he gets angry from an argument, he jumps right back to this topic and slut shames me. I dont understand why? I know myself his body count is 8 bodies (he's told me before we made our relationship official) and he's only had 2 gfs in his life but somehow thats okay? I dont ever shame him for it because, as I also point out to him, I wasn’t in the picture. I have no right to judge him based on the past decisions he's made or who he's been with. If anything, its a waste of time in my eyes. Im only thinking about our relationship and moving on forward with him.

We plan on going to couples therapy but at the moment we can’t afford it. How can I help him? I've been patient and dealt with this for so long and i’m really thinking of just giving up on this relationship. Its really taken a toll on my mental health - I already have PTSD with panic attacks and this is a huge trigger for me..
Do you believe its right to be jealous of your partners past?
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