My boyfriend cheated on me

It’s late and no one is awake and i’m in so much pain and need to express it someone. today i found out my boyfriend of over 5 years has been cheating on me with a coworker for a month. me and him have been serious for such a long time, we live together/ talk about marriage/ whole nine yards. two days ago, we were talking about what our wedding would look like. but today his coworkers husband (yeah husband -.-) texted me and told me what he knew and sent me a four minute video of texts between my boyfriend and his coworker. me and the boyfriend were at a wedding where we was the best man today and i had to run out and he tried to follow me out and we got into it in the car outside. he says he’s sorry and he was gonna tell me and that it was nothing, but i’ve seen the texts now. he’s saying he wants to change and make it work but i don’t think i’ll ever be able to trust him. in their texts, he’s saying how much he loves her and cares about her and misses feeling her and that he masturbates thinking about her. we were at a different wedding this week and he was messaging her saying he was thinking about her during the boring parts. and i was sitting next to him. and i’m so hurt and lost and i don’t know what to do. he lied to me so many times this last month and i cant forgive that, and if i can’t forgive that i don’t think i can be with him. but i care about him so much and im mad and hurt and still texting his brother to make sure he’s okay and that feels so dirty. i’m having the worst time of my life thinking about if i need an STD test because he slept with her and im worried if HES okay??!! i don’t know what im looking for here, but do you think this is has a come back potential? we had so many good times, but he has completely shattered my trust, and it’s so much worse because i’ve expressed to him that im insecure about him have female friends and specifically this coworker has been a topic we’ve talked about, even in this last month since it happened. i just can’t picture my life without him and it’s really hard to process who i thought he was with the person who did this to me