Sneaky sneaky bf

He's alllllways hiding that damn phone of his. He even sleeps with it so I won't see. But little does he know he can't bring his phone in the shower with him. I read it everytime he takes a shower and holy shit he's been flirting with 2 girls. One is his ex from 4 years ago and the other is some blonde girl.i don't say anything cause I want to get my revenge. And he always acts to inocent like he would never do anything and never tells me anything. What a sneaky fucking bastard.....how should I handle this? ( P.S I live with him and I can't go anywhere else. I have no family)