What Nancy said about allergy...it does not necisarrily have to be a new medication....or food. You can develop an allergy to anything at any time!

I've taken Bactrim probably a dozen times without problems....until the last time....after taking it for 4 days I developed hives!

It does sound more like an asthma type reaction....which can be caused by the exercise or an allergic reaction.

If this happens again you should get yourself to the ER or MD as soon as possible! Like you said, it's getting worse each time. It could get to the point where you weren't able to call for help! don't fool around with this!

And please....when calling your MD...always be specific if you're having any trouble breathing or any kind of chest pain or pressure! If the MD cannot see you, maybe a NP or PA can....or maybe you need to be sent to urgent care or ER.