Chest Infection that won't go away.

I know I am not suffering as badly as some people who post on here but I am a bit worried as am new to being mildly asthmatic, so apologies if this is nothing to worry about.

I had a cold in early May, as usual recently it went straight to my chest, ever since I have been coughing (and bringing up very sticky mucus that has been getting less and less coloured over the weeks). Had a course of antibiotics about 2 weeks ago for the chest infection and felt worse after finishing them. Feel OKish in myself now but the cough is really persistent. Take blue inhaler 2 puffs twice a day (and ad lib as required), brown inhaler 2 puffs twice daily but have been doubling up (and even tripling) the doses on advice of practice nurse. I am worse in the evenings and at bedtime and first thing in the morning, breathing very noisy (rattles and whistles etc) and as I have exertion induced asthma anyway I am breathless after even slight exertion (like going up the stairs). Haven't been back to GP as don't see the point of course after course of antibiotics if they don't work, plus steroids didn't work last time either. Can anyone give any practical advice please or suggest how long its going to take to go away as I am getting really fed up with it now!