Is he cheating on me?

so me and this guy have been dating on and off for almost a year now well it will be on the 19th and we just got back together in feb but heres where it gets weird none of his friends or family no were dating which at first i thought ok hes protecting hes self its like the 4th time we dated but this time he has this stupid chick trying to get down his pants and every time we get off the phone because he calms "hes going to bed" i call back and hes on the phone with her and tries to lie to me when my phone tells me when ur on the phone someone and like when he doesnt wanna talk to to ppl cuz hes mad he always talking to her and like sometime ill call hes cell when hes on the house phone with her and he'll treat me like crap and he like he'll let his older brother treat me like crap to he becomes this whole different person around his friends and he only acts like an actually bf when he wants something from me...... but whats really got thinking hes cheating and is he blocked on facebook and claimed he was over at hes friends ryan house this weekend but on her facebook her status said "had a great time with Zeke muah cant till we do it again" idk wait to think help!!!!