I assume you didn't just switch to PM, did you? When I first ported my number over to PM, it got stuck and I was in a similar position where text messages were not being received from most carriers (they were going to my old SIM card).
I'm not aware of any missed messages, but it's hard to say for sure since you don't know what you don't know. But so far no one has mentioned sending me anything that I didn't receive.
