Hi Catlover, I'm a cat lover too.  :)

Sounds like autumn and winter are difficult seasons for you.  Having bronchitis for so long must be painful.

One way in which MS can affecting breathing is through tightness and spasticity in the muscles which control breathing.  There are small muscles which hold the ribs together and when they get stiff, it becomes much more difficult to get a full breath.  Sometimes which is described as being the MS Hug or MS Girdle.

Another way in which MS might affect breathing is through the autonomic nervous system which control vital bodily functions such as breathing.  If demyelination and nerve damage interfere with the nerve signals controlling breathing, it can become more difficult.

Has your doctor assessed you for asthma?  I have friends who are much more affected by asthma during the colder months and it feels like bronchitis to them.  One even uses an inhaler to loosen the grip of the bronchial tubes and lessen the inflammation.

It would be a good idea to talk to your doctor again, perhaps even consult your neurologist, to find a way to relieve the breathing difficulties and pain you are feeling.  My ideas are only as another patient.  I'm not a medical professional.  But I do thank you for your question.

Lisa