I work in the health care field but I am not a Dr. My first question is are you on a blood pressure medication to begin with? If you are call your Dr. losing so much weight might have caused it to drop enough that you don't need it or at least not the same dosage. Some of my patients have this problem and they physician I work with will advise them to take their BP and if it is at a certain point (low of coarse) not to take it that day.