I agree with all the above responses - ventolin's safe as houses during pg. Apparently it's far worse for the bub if mum has bad asthma (well, so I was told).
Just so you're aware, I had a shocking cold and cough when pregnant with DS1 - my GP prescribed me a different inhaler, Seretide (purple inhaler) which worked as an asthma preventer and helped with the cough. Worth a thought if you feel bad enough to go to the dr.

Hope you feel better soon.