Asthma in Pregnancy-Please help!

Patient: Hi I am 23 weeks pregnant and have had a chest infection for 2 weeks. I also have asthma. I only use my inhalers as needed so have only been taking them since the chest infection started. I am waking up in the middle of the night coughing and on several occassions my phelm has been blood tinged. I went to my doctor and was basically told if it is viral there is nothing i can do. I also called Asthma UK and they suggested if i am waking up in the night coughing it means my asthma is not controlled and they suggested taking a short course of pregnisolone. they said this is safe during pregnancy. My doctor would not give me a short course of this steriod and said they don’t know the effect on the fetus. So I am still coughing constantly, my chest is very sore and I worry about getting enough oxygen to my baby. Is there anything I can do? If it is viral how long could it take to get better? I have had for 12 days now?