I'm drying! I need help

Hey ladies!! My fiancé and I had a very dramatic history and now I have a huge feeling he is using online dating sites or meeting with females and talking to them. Please does anyone know a way I can find out everything. Maybe hacking something. I tried checking different online dating and nothing. I tried looking at his phone but of course he's going to delete everything. But sometimes I see random selfies on his phone of himself and if I talk to him about it he will denied denied denied that's why I wanna find out by myself without telling him. Please help or if you know someone who hacks insist stuff.