Bf (21M) and I (23F) been together 8 months, been arguing over petty things, how to trust him again?

This will be a longer post and trigger warning, it mentions death/loss of a loved one. For context, my mother passed away on October 1st and since then, I’ve been having a difficult time with everything in life. My boyfriend was helping me out the first few weeks but then he started acting like I was a chore to be taken care of and that he wasn’t getting any “alone time.” A few weeks ago, I came across messages of him and an old female friend exchanging sexually explicit messages and flirting. So I made him block her because we had problems about her before. He got mad at me for “going through his phone” and said it was an invasion of his privacy. But at the time, I went through it for medical reasons to reach his parents since I didn’t have their numbers. So the situation was settled for the time being.

Fast forward to last week, we get into another fight because he wanted to play Overwatch and I wanted him to watch movies with me and for some reason, I just didn’t want to be alone that night. So I tried to get him to come out of our bedroom, but he ignored me and then got mad at me because he said the “biggest job of all was trying to make sure I don’t cry or get upset” and that he needed to “recharge.” So I cried more because he was ignoring me and I was missing my mom that night and just wanted his company.

Apparently, that night he had sent messages to one of his other female friends who is older and considers herself an “older sister” to him but they only know each other online through discord. I found the messages last night and he had been venting to her about our fight. So, she contacted me last night and then wouldn’t leave me alone and started saying things like I’m a “controlling b**ch” and other hateful things. She was harassing me and all my boyfriend did was sit there and try to apologize and not even say anything to her. He told me “don’t worry about it, I’ll have a talk with her.” He did talk to her, but it felt more like he was defending her than me. So finally he blocked her. Ever since then, I don’t trust him. He has changed all the passwords on his phone, laptop, everything so I can’t see what he’s saying about me.

At this point, I’m not even sure if we should be together. He keeps saying he’ll change and that he doesn’t want to lose me, but he constantly puts his feelings first before mine. Should we just break up?

TDLR: Gf grieving because of family loss, bf causing problems and talking to other girls either sexually or shit talking about me. Bf is selfish. Gf doesn’t trust him, need advice on what to do?