feeling hurt😥💔

Soo me and my boyfriend has hit a our 1st real rough patch in our relationship and it started the other day when we went to the store and zacbys. He ran into the store and left his phone in the car on the dash board, when I pulled off the home slide on the floor and I picked it up I see a unknown number text him "good morning. " When I seen that message I didn't want to open because it wasn't opened so scrolled down a bit more and saw another name and opened it ! I went straight to the details and saw a nude(private area)! 😥 He was headed back to the the car so I throw his phone back in the seat ! We went to zacbys ordered food and sat down an I calmly asked him to let me see his phone. I got it & went to the message and I open the message I seen earlier that wasn't open and went to details and see what looks like porn! I exit that and stroll though the message and some messages it my bf send heart eyes and other shit ! I exit and keep strolling and see a contact that my bf texted saying "this is ... 😬" but the contact was saved up under "😍😋" so that told me he got a number!!!! That shit really hurt me because before me and him agreed to be together he was my best friend someone I thought I could trust to never hurt me 😥 .. I know that we are supposed to be together forever but he didn't even physically have in course with none of them but it's still like fucking with me ! I need advice on moving forward or letting it go 😒😫💔😥😭