Am I wrong for snooping?

Shannon
Hi all before you judge hear the story first!
I'm 17 my SO is 16 and I'm currently 14+5, it wasn't planned and if happened but we are already so in love with our magic bean! 💕 I'm finishing college in two weeks and he works full time so we are more than prepared for the baby, we live together and already are saving/looking for our own place.
However lately we've been growing apart! He has become very distant, very grouchy and snappy! I didn't know what to do I asked if he was alright and just received a nod? It's really odd he's never like this towards me. I decided to do something I never would and snoop through his phone, no traces of anything dodgy until I went on his pictures....in his received file (pictures that are sent to him) was a picture of a girl he works with....I felt really odd seeing that it was nothing inappropriate just a general selfie I guess. But it was still odd?? And all of the sudden he wants to go "swimming" a lot by himself just last week he went twice in a day.... He never does anything like this and I just feel really odd!!
Does anyone have any advice or guidance? I know I shouldn't have snooped but I'm glad I did! If I hadn't what else could have been on there? 
Any advice would be great! Thank you all! 🤗🤗