Thx. I think it was an old lung infection in conjuntion with severe anemia. I think the issue has resolved. I did the following (which I think resolved it?): forceful breathing exercises, a Z-pack (6 azithromycin pills) and lisuride. I added additional 200 mg magnesium and 1/8 tsp/day potassium. The problem went away and I've been training fine for a few wks.The endurance issue sounds like you're using a lot of effort in your technique. It's worth reading the work of Peter Ralston to appreciate the benefit that effortless technique can give you in terms of enduring that sort of punishment.
Yes I agree with effortless technique. Looks like Ralston writes cool books!!! I am super-duper soft style and technique focused. My original teacher was/is a zen monk who put us through the ringer to train softness and "internal" energy.