Should i tell him?

Me and my bf have been together for 7 months. He is realy nice and everything a girl can ask for. I know he texs my friend because i went throug his phone with out him knowing it said"your mean to her" she txd him that?!!! i want to ask him but im embarrace he askes why i went throug his phone? i know i have the rights to im his gf but what if he turns it back to me and question if there trustworthiness in the realation ship?