Thanks for all this advice - I am going to see if my usual Spring allergy/asthma routine works - if it's not better by Monday, time for a specialist.

My guess is that it's an allergen, (mould) not EIA, but I think I need a Dr. to do some real tests!

I am lucky that I don't have wheezing and respiratory infections - lots of people suffer much more seriously than I do.

I think an element of this is that I have never pushed myself physically this much before. I am in the best shape of my life, but why not make it even better.

Thanks for everyone's advice - I may print some of this out and bring it with me to the Dr.!