I have a flu for 3 years and asthma. Ihave a lot of mucus that affects on my head. This mucus is white, I always throw mucus and I have a dry throat.?

See your doctor. Problems like these can only be correctly handled by your doctor in person. He/she needs to listen to you, perform an examination and possibly run labs or other tests. That's the only way he/she can find out what's going on and what to do about it.