how do i get past partners emotional affair

2 years ago i found out my bf had been textn a coworker ALOT. They had also stayed after work to talk and he admitted hed been to her house to help her with her studies. The texts did not insinuate anything sexual except 1 where she said 'i want to kiss you' to which he said 'im smiling so much-my face hurts'. He had said stuff like 'ive never felt this way'. I was crushed. We had been together 10years. He since has cut off contact, changed jobs after a year of me questioning everything and allows me access to phone etc. He doesnt even turn phone on at weekends. I just still at times think back and wonder if more happened. If those visits were sexual or if he lied when he went to sports clubs etc i couldnt bear it. He denys anything like that and as i said i didnt SEE anything of that nature but it plays on my mind, i remember him sayn he met her after shed been to the gym once and now out of nowhere it came to me that it must have been another time other than after work?? He says im lettn it rule me and nothing happened. How do i let it go n stop dwelling