How do I get rid of my cough?

I have this nasty cough that comes from a cold. I am taking Robitussin cough and chest congestion DM Max and im also taking Robitussin cough liquid gel caps and i can't stop this cough. I really need to stop this cough SOON because i have very very bad asthma. So bad, that i could be hospitialized if I don't get this cough to stop because it will act up. I need something to stop this cough. Please help me!!!