Is he cheating on me?

i have a boyfriend weve been together for a while and i think he may be cheating. first of all i have never been a jealous girlfriend before to anyguy and i wasnt with my current boyfriend until a couple months ago. i know for a fact that he doesnt have a history of cheating on his girlfriends, and he is not a player. although, a while ago he kissed another girl, he confessed to me about it and he cried and begged for me to forgive him, i brokeup with him but a couple of weeks later we got back with eachother because he did alt to prove to me that it was a mistake and he was sorry and he really cared about me, and i love him so i gave him a second chance. now by what i know he hasnt cheated on me since but in about the past week or two his behavior has changed a little to me. if i text him on my phone saying "hay babe" or something like that he wont write back unles i say " its alexandria" to me that seems like he has other girls calling him babe. he also has been hanging out with a whole different big group of friends and he goes to parties with them and i have no idea who they are but i know there are girls in the group. today, i talked to him about my suspitions and i asked him straight up if hes cheating on me. he looked away, paused, and then shook his head no. lieing much??? to me that sounded and looked extremely suspicious. is he telling the truth?