Is he cheating on me? should i leave him?

[PeppermInt.]

I'v been dating this guy for four months now but some things hes doing are sending red flags. We got in a fight about a month ago and he blocked me on Facebook and hasn't unblocked me since. He has a lock on his phone which i found out the password and went through it and found that he was talking to two other girls and telling one he missed her he told me he was drunk when he sent that and got mad at me for looking through his phone now he changed the lock and wont let me near his phone. This really bothers me and iv talked to him about it and he wont unlock his phone and he just keeps telling me he doesnt get on Facebook but i know he does since some of my friends are friends with him on there. Another thing is he never really likes kissing but he likes to have sex and thats just really weird sometimes he'll kiss me on the cheek goodbye. I dont really know if hes cheating or just wants his privacy hes always told me if he cheated he would tell me. We spend every night together and during the day he works 9-6 so i dont know when he could possibly be hanging out wit other people.