Am I paranoid or could he be cheating on me?

My boyfriend and I have been dating for almost five months. We have been so happy together until recently. We have been arguing a lot more and it is almost always over something small or stupid. Today I went through his iPhone. I do it all the time and I always do it in front of him so he know. A lot of the time he takes my phone and goes through it also just for fun. Well, today when I went on his phone I went onto his myyearbook. I went straight to these messages that he had. Two said " Thank you. " from two different girls and then another was from a girl flirting with him and asking him to skpe her. The part that got me was that all of the messages that he sent to these three girls were deleted, so I have no idea why the two said thank you and I don't know if he started the flirting with the other girl and I don't know of he actually skped her. Then it became worse when I looked at his profile and it saw it was under a fake name and the profile picture wasn't even of him. It was a picture of a nice sports car that he doesn't even own. He is such a compassionate, and cute guy. I'm completely in love with him. I don't want him to be a liar and a cheat. Please help me. I need to know what to do and if he is a cheater and liar.

You are his security blanket…
he is discovering that their are thousands of girls out there…
these texts are his way of testing the waters…
you are too young to be serious…
let him go, before he leaves you hurting…
best you be the dumper not the dumped on

Uh… Well, if you looked at his profile and it was under a fake name, I'd say you're dealing with a liar and a cheater. Sorry you don't want him to be one. Won't make him not be one.