My boyfriend keeps texting his ex's? Is it me or him who is wrong?

I met my boyfriend one year ago . As usual everything was amazing. But I knew he had a reputation for cheating.. so I was very carefull. The weeks went on and everything was brill then I noticed his phone was constantly beeping with texts and when i would ask who is was he would say his best friend. Til one day he forgot his phone and I looked at it .. i know I shouldnt have but I did. There were messages from a girl I knew had gone abroad for the summer( His Best friend's recent ex) and she knew we were in a relationship. Messages like "I miss you" ... my heart dropped to the floor as i read it.I also got onto his facebook where I found messages arranging for him to collect her from the airport and flirting needless to say he changed his password straight away but this made me suspicious ... was it still going on after I confronted him??? But she was not the only one he had also been meeting up with an ex and denies anything happened! (But I know his reputation).I will never know but we got passed it and things were good again. Untill recently ..... When he left his facebook open by accident.... and surprise surprise a message to another ex at 2 in the morning telling her to ring him !!!!!! Its getting old now but he always has an excuse (Not being mean but this poor girl must have no family left because any time I catch him hiding texts to her he says someone in her family has died which I know is not true deep down but I cant be so insensitive and say stop lying!) Like why would he have to Lie I could sympathise with her too if it really happened.... Im not that bad I wouldnt begrudge her just because she was an ex.... Yet again we got passed it ...... and even more recently his ex (he had been with for 4 years ) and on and off after that.... The kind of love/hate relationship where they were either killing each other or madly in love...... but when he moved on she couldnt let go completely... ringing him for drives ..... for chats ...calling him his sista from another mista so he would add her as family on facebook! Is it just me or am I wrong to feel just a little intimidated because he says its just ~Girls name~ and I have nothing to worry about even tho he cheated on his last girlfriend with her !!! I am an understanding person but recently he has been hiding phonecalls and texts ...... like texts at 2.10 in the morn just minutes after I left his house and his bed!!!! Booty call???? no? I just don't know ! I know im no angel ha ha......but I did learn from my mistake.... what should I do because when I confront him I just get another made up story !! His friends say they have never seen him fall for some1 lik ehe has for me but it doesnt seem to me !!! I need help !!!!!