I have really bad asthma as well. Before I started seeing my Asthma Specialist (Dr. Perlman out of St. Barnanbas in Livingston), I was taking 120mg of Prednisone a day. If you've ever taken Prednisone, you know I was miserable. He controlled my asthma with Singulair, Advair, Flovent, and Zyrtec (lots of meds!) He also diagnosed me with Gastro-Esophegeal Reflux Disease (GERD) and put me on Nexium. Turns out the acid from the GERD was making my asthma worst. He's controlled my asthma so well, that I have not taken Prednisone in over 3 years.
During my pregnancy he swithched me to Zantac (for GERD), Pulmacort, and Rhinocort. I did have some tightness here and there and had to use my rescue inhaler (Proventil). I tell you all of this because it was my GERD that was causing my asthma to act up. GERD gets worst in pregnancy. Are you seeing a specialist or your PCP? Most women get GERD during pregnancy and some do not get diagnosed correctly. If you don't see an asthma specialist now, please consider Dr. Perlman. He's wonderful, and has been named Doctor of the Year in the past. Also, make sure they rule-out GERD and treat you properly. Good luck.