Question/advice

So my boyfriend broke up with me last month beachside he was depressed and shit but during our break up he got his dick sucked by another female from his job (mind you i had no idea about this until today). He didn’t know her at all nor he had never talked to her. After that night the next day he called me and ft me telling me we were gonna get back together, and so I believed him (we are together now) but after we got together I felt something off and noticed small changes. Today we went to the mountains with family and he left his phone with me because he was playing volley ball and well since I had noticed him being weird and doing small changes I decided to go through his phone. At first I did find anything so I just put it away but something in me just needed to find something and I went to his deleted pictures in which I found pictures of a girls ass which was facing up in his car so basically he got head and took pictures. I honestly couldn’t believe it. I started shaking and my blood boiled because I was hoping it wasn’t what I thought it was. I tried to keep myself together until he stopped playing so we could go on a walk and talk. He ended up admitting that he did get his dick sucked by another female from his job when he broke up with me. I didn’t know until today and I am so hurt that he did that. Yea he broke up with me and we weren’t together at the time when it happened. He said it was a mistake and he regretted it afterwards. He said she couldn’t make him cum, that he mad himself cum. I still don’t understand he did that but he says it was because I wouldn’t give him enough head. Which sounds so crazy to me because all I did was please him. We’re still together rn but should I even be hurt? We weren’t together when he did that but like it hurts. I broke down infront of him. I have never cheated on him never talked to another guy. I’m still kinda sad but honestly idk what to do. I really love him and he says he loves me but how will I know he won’t do it again. The trust I had with him is now broken and I can’t trust him. He begged me not to break up with him but honestly idk rn. I really do love him. Was it wrong for me to be mad at him or am I just crazy? Lol is what he did considered cheating??? Or not?