I have allergic asthma, and I have symptoms like yours. I have never been a smoker, but I have a lot of phlegm and I have seasonal allergies. What helps is to treat the allergies that are creating the phlegm. I do allergy shots, and use over the counter antihistamines. I also had food allergies and intolerances, and foods can also influence how much phlegm you have. It's easy for my allergies to build up enough phlegm that it crosses over into a bacterial infection, and I think this is common for asthma because the phlegm sets up a good breeding ground for bacteria.

Thinning the phlegm helps you expel it and generic Mucenex works well for that. For me, it usually starts as sinus congestion first before it moves into my lungs. Doing a regular saline nasal wash does help prevent sinus infections. It may be beneficial to work with an allergist, and treat a potential bacterial infection. My doctor gave me some anti-bacterial ointment and I use a bit of it in my nose at night when the infection is starting. After a few days, it clears, and this does generate phlegm while the lungs are flushing out the problem, but after that my lungs are clear. You can be walking around with a low grade bacterial lung infection and not know it. One of my signs is that my resting heart rate goes up a little bit when I have a lung infection so I notice it when I stand up or go up a flight of stairs.

I also use HEPA air filters in my home and avoid my asthma triggers. Those include fragrances, smoke, and allergy triggers like seasonal molds. Molds have been found to cause swelling in the airways in addition to an allergy response, so they affect me a lot. We are careful to ventilate bathrooms after showering so the towels will dry and not mildew in the humidity. You may want to investigate any potential places for water leaks such as a wet basement, or excess humidity in your home because that can affect you without your being aware of it. Also if you miss an apple in the kitchen that goes bad, it can grow some mold too. The spores are everywhere just waiting to land on something moist where they can grow.

Keep exercising because your lungs need to move to be able to expel phlegm. Some of my issues are physical because one side of my chest wall is too tight and doesn't move as much, and when I get a chest infection it always starts on that side. Some of my phlegm had also come from an unusual source because of an immune response to foreign materials in my body from dentistry and surgical plates for a broken ankle. When those things were later removed, and I no longer had metals in my body, my asthma improved a lot and I had a lot less phlegm in my lungs. There are doctors who treat things like that called environmental allergists and here is a link to a provider search: https://www.aaemonline.org/ You can look at this website to learn more: https://www.ehcd.com/

With allergies, everything adds up, so if you reduce what you can, it helps. Do you have any thoughts on what changes you can make that may help your situation?