Need advice, break up or no

I went to take silly pics to post on my partner’s snap story and saw that he sent his friend this picture of my butt in see through underwear 2 weeks ago.

I confronted him and he said at the time he didn’t think it was that big of a deal but he is genuinely sorry and wants to be given a second chance to build the trust back. I told him he disrespected me, demeaned me, violated me, and embarrassed me. I told him I lost all trust in him because my body is only for him to see. The thing that gets me is that he knew I was traumatized from an ex posting nudes of me when I was 15 so I feel betrayed. I told him I needed some time to think about it but I just cant understand his f*cked up thought process as to why he thought it was okay. Im also a month pregnant with his child and we’re engaged and were going to get married in 2 weeks, which I’ve told him I want to push it off now.