cheating?

Okay, so I've been with my boyfriend for awhile and we are moving in together in less than a month and we are also trying to conceive. But he got a new job and is making me a little nervous. After his first day, he came and said he had some girl who had been flirting with him and was constant watching him. I brushed it off because he didn't do anything back. But now he keeps mentioning her slightly just,"Hey guess who I work with tonight?" And obviously I know, they originally did not work the same shifts until recently and now he goes in earlier to work and is asking me to pick him up about half an hour or later after his shift. He has also been hiding his phone more when he gets a text. I'm just nervous and need some advice. Thanks!