Humidity-triggered harsh cough, reasons?

[ChemicalChaos]

For absolutely ages now I've had an awful cough that is triggered by humid environments, such as stepping out of a long hot shower. It literally feels as though I'm about to choke, and I end up hacking away for ages. Eventually, either a) it goes away after going to a cooler, dry room for a while, or occasionally b) I succeed in bringing up the large, choking glob of really thick mucus from way way down the bottom of my throat. Its understandably very annoying and concerning for both my flatmates at uni and my parents at home when it sounds like I'm dying every time I step out of the shower.
Interestingly, I get pretty much the same symptoms if I'd had a lot of caffeine such as a few cups of coffee whilst working late into the night.

Although I must had had it nearly a year, it seems to have been getting slightly worse recently. I dont smoke, I eat healthily (well, for a student), exercise by cycling to uni every day, dont have asthma and dont drink excessively. Has anyone got any ideas please what could be causing this?

Thanks in advance,
Matt

[C0ffin D0dger]

Have you been vaccinated for TB?

No blood in it I assume? Could be anything really, if you're concerned enough go and see your doctor. They'll have a listen to your chest and if concerned enough send you off for an X-Ray. That would show anything dodgy going on.

[ChemicalChaos]

Nope, no blood but it is quite yellow compared to normal phlegm.
I've had all my vaccines over the years so I am TB-proof as far as I know.
I keep meaning to get it checked out but it never seemed that serious until recently and I'm always so busy