can I ask to see his phone?

So I'm just wondering if it's ok to ask my boyfriend of 5 months if I can see his phone? I don't want to sneak around I just want to ask him. I don't think he's necessarily cheating but I think he's talking to other people. So is it okay to be straight up with him and tell him I don't want to sneak around that I just want to look at his phone?