Couldn't breathe

So I am 17 weeks 1day today and when I woke up I couldn't breathe. My throat felt really tight so I grabbed a bottle of water and ran outside. Being outside helped and I have to say my house is quite dry due to the winter. But it's never got so bad that I had problems gasping for air. I don't know if it's just because I'm pregnant or what. :/ should I phone my doctor??