Boyfriend cheating?

Annie
so I was in the ar with my boyfriend the other day going out for a lovely night out with my man. We use his phone for a gps, anyway he checked his phone and there was a text message and another chat icon notification which clearly wasn't FB or anything. He looked at me straight away and wouldn't push the notification bar down (his phone is Samsung) he then quickly cleared it so notifications were there anymore. IM angry at myself for not being like "wtf is that" 
Me and my boyfriend did meet on a dating site and as soon as we got into a relationship all of them were deleted. He said he still has them on his phone "but never used it" now what the flip do I do. I don't wanna snoop but I think he is cheating? Or am I just jumping too far into this... told my mum about it she said I need to talk to him. Is it bad that I wanna make a fake account and pretend to be someone else and go onto a dating site which I know he uses and serif I can find him? I'm so over immature relationships, I want something serious. I just need yall help ladies. ( I'm sorry if this makes 0 sense)