Why would he say he's coming over, not show up, and then ignore my calls?

I've known this guy for about 2 years. We've been talking on and off throughout the time we've known each other. When we first started talking he would hang around a lot but he was sorta pressuring me to have sex with him. After awhile, he gave up asking me about it and seemed sorta happy that I didn't give in. He also continued to hangout with me. This past summer, I was finally ready to have sex with him and he exhibited symptoms of erectile dysfunction and seemed really embarrassed. We stopped talking for a little and then resumed not too long ago. Well now, we've gotten much closer. He invited me to Thanksgiving dinner (I didn't go). And we've been spending more time together. I even let him borrow my car. Last week, we were in the car and his phone rang. He told the guy he was with his "girl" and that he would call him back. It was the first time he had referred to me as that, so I was shocked. A week later, I phoned him and he told his friends in the background to quiet down because he was on the phone with his girl. He proceeded to tell me that he was on his way over and that he would call me when he got close. He never did. The following day, I text him to ask what happened and he never responded. He also stopped answering my calls. I'm not sure what could have happened. I thought everything was fine. I should add that I hinted that I wanted us to be more intimate and he said that he'd prefer we go out and do stuff. Could he still be ashamed about what happened? But, then why would he say he's coming over, not show up, and then ignore my calls? Its like he's acting very hot and cold...