The first thing you need to do is quit smoking. Some people are more sensitive then others when it comes to chemicals. I know I was. I now have COPD after smoking 30 years. I quit 20 years ago.
Seems like some people can drink and smoke all their lives and they are fine. But for some of us it's a big problem.
Good luck..
It is quite possible you have a staphylococcus infection, since you are having thick yellow (key -yellow) mucous coming up. Much as you don't want to go to a doctor, you don't want to develop something like walking pneumonia and die either- please take care of yourself and go in to your family doctor and ask for a sputum culture to see if you need to be on antibiotic?
Additional things would be to suck on zinc lozenges, take an over the counter expectorant that loosens secretions to help you get them up, take vitamin ester-C (zinc and the C to help bolster immune system), drink plenty of water, eat yogurt with live cultures, etc..
Also, the fact that you are getting more when you lay down, as would be normal when you are sick for mucous to pool in the lungs: you will want to have your head of your bed elevated at least 45 degrees.
Additionally, smoking is a risk factor for developing acid reflux, which also can be worse when lying down and can GERD can lead to coughing, which could compound lung irritation. If you notice a sore throat, heart burn, belching and the like, you might try an over the counter medication for acid reflux to see if it helps at all as well. But bottom line, is those doctors got all that training for the purpose of helping people just like you and the good ones are best equipped to test you, properly diagnose exactly what is the source of your trouble, and thus prescribe for you the best treatment medicine has to offer.
My mom just had about the same thing.It was fluid in her lungs,we went to alot of doc appts and COPD was one of the thing one doc said she might have.You will know with alot of shortness of breath.She used Musinex,Vicks44,and my dad made her quit smokeing.Also try some allergy Meds for nasel drip.Cut back on a few ciggeretts and try some walk in the fresh air its nice out.