I'm with Shapinglight, you might get checked for asthma.

Funny thing about pregnancy. You obviously know your body before you get pregnant, then everything goes haywire. After you give birth, things settle down some, but it's like so many things changed, you don't really know your body so well any longer. It was like that after both of my full-term pregnancies. I had to get used to a whole new me each time. So odd.