My boyfriend and his ex talked on Myspace, and he didn't mention me. What does this mean?

I was bad, and I snooped. My boyfriend and I have been together about 5 years. His ex messaged him on Myspace. They dated back in high school, years ago. She was his first, but she cheated on him and they broke up. Recently, they messaged back and forth a couple times on Myspace, and it was all just small talk. But, two things bothered me about it. 1) He was so incredibly nice to her, telling her how great it was to hear from her, and he was so glad she was doing well, yadda, yadda, yadda. He always seemed bitter and like he wasn't interested in a friendship with her, so why all these gushing remarks? 2) He didn't even mention me. I think she even mentioned her new boyfriend, but he said squat about me. (This is the part that really bugs me.) When I confronted him about it, he said those messages were leading up to him telling her off and saying how happy he is now with me. He said he was only nice to make sure she would read his responses. This rung false to me, like the biggest load of BS I've ever heard. What the hell is going on?