My Feet And Ankles Swell Every Time I Overdo Any

My feet and ankles swell every time I overdo any physical activity. I have Fibromyalgia and an unstable spine so it doesnt take much to overdo! Housework for more than an hour or so will do it. I just had the test with the cuffs on my legs(abt i think it was called) which I was told was "abnormal" so then Dr. sent me for a Heart Echo which the technician indicated was normal but I haven't gotten results from the Dr. that actually reads results yet. The tech also indicated that the heart echo should not have been the next test but a venus(sp) instead...I'm so confused! What's your advice for my next step and shouldn't I be very concerned with the feet swelling? I've heard horror stories like amputation, etc...if not treated..thanks in advance, Rose M.