I found with both my pregnancies I was very breathless even early on. I would however see your dr at your next antenatal visit probably not urgent unless its accompanied by blue around the lips, fingernails etc, chest pain etc. Maybe your asthma medication needs to be changed or you need to be on medication like ventolin or seritide if your not already. Cause of the extra blood in pregnancy which will only get worse as your pregnancy progresses your heart has to work harder.

Hoping it eases for you.