What is going on with him?!?

OK, Well let me start off by saying that I am in a long distance relationship with my bf of a year this month and we do see each other every weekend only being 2 hours apart. Anyway, let's start from the beginning....about 4 months ago, I had asked my b/f for his myspace pword so I could add something to his page because it was just easier if I did it rather than he because I know how to work the different codes. ANYWAY, so yeah I'll admit I was feeling nosey so when I was done I went through his messages on there just to see I could find anything. While I was doing this, he was on the phone with me and he obviously could tell that I was really into what I was doing because I wasn't really talking and he kept asking me what I was doing, well it just so happens I fall upon several messages from a girl who lives about an hour from me. I don't know her, and neither does he, apparently he just saw her myspace and started talking to her. As I read on, the messages were getting flirty, and the girl knew he had a g/f and she even said "wouldn't your gf be P.O if she knew you were talking to me?" and he replied saying "I'm not doing anything wrong we are just talking"..so as I'm reading on, I notice that some of the messages are dissapeering..till finally I go to read the next 1 and the folder claims to be empty..he signed on and deleated all the messgaes from that girl as I was reading them. Mind you, in these messages he even tells this girl that he is taking me to a really nice resort for my b-day which was 3 days away...so anyway, I flipped out on him and didn't answer my phone for 2 days. So, I wound up forgiving him that time and he swore to me that he would never do that again and I'm all he wants and whatever. That was Strike 1. So now, he and I are on the same phone plan and I've just lost a lot of trust with him, and on my account I can view all the numbers that are being texted and called so I've seen on my bill that he's been texting and recieving texts from weird numbers..so I confronted him and told him straight out that I have access and can see all this and he told me that this girl was an old friend from high schools g/f. He barely talked to this guy, and he rarely talked to her, and some how she has his number? How? He claims that someone from his hometown could have given it to her. And that he's not talking with her anymore because it seems like she wants more out of this friendship. Anyway, I felt this was too odd, so I texted this girl a few ?'s and she told me that they are just friends and I told her that he felt she wanted more out of this friendship when I confronted him about it so he's going to stop talking to her, and she flipped and said well that's funny cuz last week he said he wanted to f- me..SO, then I call him up and flip out on him again, and he said she's full of it, and he wound up calling this girl and yelling at her apparently cuz I got a txt back from her saying she was just saying that he never said it and she's sorry, because all she ever wanted was to be cool with him. So now at this point I'm confused, and I told him I didn't want him talking to her anymore because I wasn't comfortable with it, and obviously for good reasons. Strike 2. Then this past weekend I see that she texted him at 2am saying that she's drunk..why would she feel the need to text him that after all this drama? She knows I'm his girlfriend..why would he care? I told him he needs to stop talking to her because I'm not puting up with this crap anymore, this is it..strike 3 your out. He says he is being polite and answering when people (girls) text him, he can't just say "I don't want to talk to you anymore" I'm not asking him to say that, either kindly explain to them, or just ignore them they will get the hint. Not like it matters anyway he barely knows her. Then just this morning I went on and saw that she texted him for a good hour on Sunday, AFTER I had left, and I asked him why he was texting her and not me and he said "that must have been when I was on the phone with you." So I'm like, "wait a minuet, your texting this girl while on the phone with me???" And he's like "she just asked how my weekend was"..SO! I know this was extremely long, but I needed to get this off my chest and maybe get some answers.. what should I do or say? I know there is a trust issue, obviously, but i'm just really confused. Did I act unappropriate, or am I just crazy?! Help!? :)