Many worries

I can’t help but worry about the loyalty in my relationship. There’s not really any signs I don’t think. There was a time in the begging of our relationship where he broke the loyalty and my trust. But right now I mostly worry about his current boss(a female). My boyfriend is 29 and I’m 22. His boss is a little older than me and closer to his age. He seems too friendly with her. He claims she’s “just his boss” but messages her outside of work all the time, jokes around with her, etc. He told me when I first started worrying that he just talks to her about work but that’s not true. I’ve seen some messages quick when he’s on his phone around me and it just seems flirty sometimes. Maybe he doesn’t realize it, but it really bothers me. We live together and I talked to him about it this morning and he told me I have nothing to worry about. But its just still in my head. She has a reputation of being one to mess around with any guy she can, even if they’re in a relationship. I just hate it. I hate worrying so much. I just want him to act like she’s just a boss and not talk to her all the time. She’s training him to be assistant manager which means he’s constantly by her side every day at work. In my head she’s so much prettier than me and skinnier. He told me he didn’t like her like that and I trust him but it’s just hard. I think maybe what happened in the beginning of our relationship has something to do with my worrying. I don’t want to ask him to see all the messages or ask him to stop talking to her and treat her as just a boss because I don’t want to seem like the “crazy girlfriend”. I get scared of communicating . Does anyone have any advice on all of this? I’d just like to stop worrying so much.