I'm 22 and hav severe asthma. I'm on combivent, albuterol inhaler and neb, spirvia and singular. Phenergan (promethazine) DM not stopping SEVERE coughing?

Steroids and rx GERD. I agree. Treatment of your GERD which can lead to microaspiration and bronchospasm, is a high priority. You may need a course of oral steroids prior to starting inhaled steroids. I would advise pulmonary testing and follow up.
Different medication. I don't see any inhaled steroids among your medications. Also, you mention GERD but no medications for it. If you are not being treated by a board-certified allergist/immunologist or pulmonologist, you should see one. Start by GERD precautions, elevated head of bed, no food or drink for 2 hours before going to bed. You may need prescription medication. See a specialist! Also, go to www.aaaai.org.
See below. That is a strange combination for asthma. You need to be on an inhaled steroid at least. I would discuss this with your pulmonologist.