Anxiety after loosing trust in my boyfriend

My boyfriend a couple weeks back told me he was going to the gym…what he was actually doing was hanging out with a girl he used to know in junior high. She used to have a crush on him and continues to have a crush on him to this day. She’s very obsessive of him, and it really weirds me out. She ended up kissing him but he said that he did not want it and that he left immediately after. I feel absolutely betrayed. He said he will never lie like that again. He said he wanted to make his own decisions without me stopping him from doing things. In a way I guess he felt like rebelling, especially because he said he thought it would be an innocent meet up. She said she had something very important to tell him and that it had nothing to do with relationships and that she understood that he was taken. Ever since I’ve been having bad anxiety. We’re his intentions completely innocent? Will she show up at his work? Will he lie again? Am I not enough? He has been really great at reassuring me that he has no interest in her and wants to build a life with me but I can’t seem to recover. I don’t know what to do.