I have a fast heart rate (for me) 100bpm. I have been hot all daylike everyone but now feel cold. Temperature 38.3, banging headache, cold hands and feet. I have a blood pressure machine and and its 155/89. I spent an hour in the shade from 1-2 pm (work in a school) but otherwise have been indoors. Any ideas would be great. I have just taken ibuprofen as this has come on quite quickly.