Need relationship help please!

Ok the guy I have been seeing for 6 months & who was supposedly in love with me has been pulling away for a couple of weeks. When I ask him what’s wrong he says I always think something is wrong. We went out and had some drinks and a girl kept texting him well past 0130 and this is a girl who is a known slut. When he went to sleep I checked his phone which I shouldnt have and found alot of bad stuff, he had been telling her how beautiful she is and how they felt so good together etc. Well he doesnt want to be with me anymore simply cause I checked his phone, now tell me if u were truly in love with someone that would not make u not want to be with them right?