Should I leave him

My boyfriend had put his phone on charge and as his was 100% I decided to put mine on charge as I left my charger at my parents house I noticed that there were messages from a woman who he saved as babygirl I went to see what all this was about and I found out on his phone pictures of her boobs and her in her lingerie I was so upset I confronted him about it and he said his friends were playing a joke but it definitely did not look like a joke as every few days he says he goes on vacations with his friends but when I ask his friends they said they haven't been on trips also when I ask if I could go with him he seems very nervous and worried like as if he is hiding something 
I don't know what to do should I stay because I really love him and that we should work through this or should I leave? as he's just using me