Help me ladies!!!! Husband cheating??

I woke up at 7 this morning to feed our daughter and his phone was in the bed. Been noticing him not plugging it and and keeping it with him but it has been forever since I've actually looked at it. All I did was open it up and there was a msg from a girl on fb. All it said was school. And all the msgs before that were deleted... Now this isn't just some random girl. She works at the store right down the road from us and seriously flirts with my husband everytime we go in there even if we are together. And I told him about a month ago that I wasn't very comfortable with that and of course oh I have nothing to worry about and now this. What do you guys think?!? Help please. I don't even know how to confront him about this.