Can a better prescription be given for the built up mucus in your lungs that is making it feel like you can't breathe, because the nebulizer, ashma pump and musinex is not working?

Fluids. You need to drink enough fluids and stay well hydrated to mobilize the mucous and thin it out. Drink more fluids along with the mucinex (guaifenesin). See a physician if the mucous is discolored, green or bloody.