My boyfriend is sneaky

so we've been together since June 2013 we had our son Feb 2015. anyways he's sneaky as hell. we've had our fights he was talking to other girls until my son was 6 months old and I didn't know until I found this secret phone he had one day when he fell asleep. I wanted to go crazy on his ass. so we split up and then ended up moving in together in October 2015. so after that we haven't had any other problems with arguing . but we're in the process of buying a house now. so these past few months he's been very sneaky with his phone he keeps it on him he puts it under his pillow at night time and never lets me touch it. if I grab it he chases me down like a fucking ninja.