Oh Lisa, I feel for you - we just did that, which is why I haven't posted much in the DDC and stayed lurking when I had time to play on the computer. Moving and pregnancy are an evil combination! I joke that I'll have everything unpacked and set up the way I like it in time for about an hour's rest before the baby comes.
To the OP, yeah, it has happened to me a few times while laying down. If I change positions (like switch from my back to my side) it seems to make it better. Are you congested at all and is that making it hard to breathe too?