What do you think that I should do about this ?

ok my boyfriend is sleep and I see in his phone that a girl texted him saying what happened to you last night and to come see her today but he with me right now and he texted but you neva answered the phone or called me back. I'm I wrong to be looking in his phone should I be mad and break up with him we always break up and get back together and I'm 7 months with his child.