advice?

my boyfriend gave some girl that works at this taco his number... he says it's something to not worry about but when I asked to see his phone last night he wouldn't give it to me bc he was deleting her messages and others... he said it was innocent but I find it disrespectful to have given her his number anyways knowing her intentions with him. I literally feel like I'm going crazy tryin to wrap my head around the fact that he might actually want to talk to this girl hence why he gave her his number... she had it before but he changed his number when he got a new phone but he gave her the new number. I want to trust what he says and does but it's hard given the situation