Do I ask to see his phone?

I think my bf is talking to other girls, but when I ask he denies it. It’s just been too many times where he’s been so damn suspicious. I want to know if I’m right or wrong..but I don’t want to ask to see his phone cause I don’t want to get to that level..then again curiosity killed the cat. If I’m wrong and he lets me see it, he’s going to hold that against me. Then again the other day he confessed to looking through my backpack, snooping around..