How do i get rid of flem in my throat caused by asthma?

I have asthma and was born with it. Ever year around the same time i get bad symptoms, flem in my throat and other stuff, due to my asthma and allergies. I have been to an allergist and he has given me different medicies that work temporarily. Also, my aunt who is an herbalist has given me some things. I went a year using her stuff then tried the allergies stuff.. now im using both.. mostly the allergist perscription meds. None of these effectively get rid of flem. The flem makes it hard to breath and fall asleep at night. Can anyone help?