Problems with imessage iPhone

I have been having problems with imessage over the last couple of days. I finally after months of having my phone fixed the imessage caller ID to show my number instead of my email. I've noticed that since then I've had issues with it. My boyfriend has an iphone 4 running on iOS5 and I have a iphone 4s running on iOS5. Before I changed that his messages was sending fine, they had a delay on them from time to time. But now some of his messages aren't even sending to me and it's even showing above his message that it sent as a text message instead of an imessage. My question is, is it my phone or his phone? thanks