I live in a moderate climate yet I have had a constant cold 4 6 yrs. This is not hay fever, what could it be?

I find that if things are going well at work / study that I cough less,
as apposed to other times. Could this be stress related? If so how does this effect the immune system exactly? What other possibilities might this be? ( I have been to the Doctor many times and I am tired of being prescribed hay fever medicine - when this is not hay fever)

go on a trip a see if it goes away

When you say a "cold", do you maybe mean just a sore throat, runny/congested nose, throat phlegm, and a cough?? Have you been tested for HIV?? Seriously, they could be symptoms.

Do you smoke? Are you allergic to cats or dogs? Are you reacting to mold in your home or worlplace?

Try a new doctor.

It could be allergies, or an infection of some sort. Go back and tell your doctor that the hay fever medication isn't working. If you still aren't satisfied; you can always find a new doctor for a second opinion. :)

Stress definitely impacts on the immune system. You know yourself that when you are overtired, overworked, or stressed out, you are much more apt to come down with something.
There is, however, another possibility. You could have a border line allergy to something. This is an allergy that you can normally keep under control, but when you get stressed, it's going to get the better of you. And a 'cold' can be one symptom of an allergy.
Try keeping a record of things like precisely when your colds break out and look in the 12 hours previous to see if you did anything different, at anything different, wore anything different. Allergies can be really tricky to track down, but if you can find a common trigger, then you may be able to solve your problem.
Good luck!

The huge increase in the U.S. in allergies and asthma, especially among the very young and the very old is directly related to industrial air pollution.

Oh honey! How long has it been since you have flushed all the toxins out of your body? Go to a health food store (Sometimes walgreens will carry it) and get any detox product they have. For colon or intestines.
Then go to a local massage therapist and ask for a lymph drainage. You won't be sorry! I had a client with the exact same symptoms as you and this worked wonders for her!

If you've had the symptoms that long its probably either a food allergy or enivronmental allergy where you are exposing yourself to the culprit on a daily basis. I would suggest going to allergist for testing.

Seek a natural therapist, you may need to adjust your diet.
Yiu may also benefit from an allergy test.