Adrenal gland & Low heart rate

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Hi I'm Stephen, lost 287 lbs in a little more then 2 years, I know weigh 263, yep that means I was 550!!!! Here recently I've had my sugars crash throughout the day, get dizzy bending over or standing too quick. Also my recent EKG shows a heart rate of 40 :-( I work out for 2 1/2 hrs M W F, from jogging in the pool for 15 mins, 1 hr water Zumba aerobics, work the weight machines for 2 sets total of 12 machines. I jog more then a 1/4 mile and walk the rest for a total of 1 mile on the indoor track. I drink Unjury protein shakes, avg 100 grams of protein a day, and 80 oz of fluids, on a 1900 calorie diet. Dr's have given hydro cortozone for the adrenal gland, and Dr's say "it's just your body has to catch up with your new weight". Hmmm Any advice?