I am 55 year old female slim eg 5 4 and weigh 8 stone to 8 stone 2 pounds. I go to zumba classes 3 times a week- eat a relatively healthy diet- loads of fruit and veg but like cheese and eat more meat as husband won t eat fish. I walk whenever I can etc , don t smoke but drink wine twice a week. Have been feeling dizzy. My BP is normal but my pulse has shot up from late sixties to nineties. What is the cause. I also am experiencing tiredness hours after exercise.