They probably checked your thyroid levels when they did the bloodwork but its worth asking. This can cause your heart to race. Im going through something similar in that my heart rate is high, my bp is high & Im getting very breathless. Been given a blood thinner jab in case of clot on the lung & had ct scan yesterday which showed fluid leaked into pleuratic cavity around my heart. No known cause so been told its probably a virus. Valium is a wonder drug. It relaxes you and makes you so laid back & carefree I love them. Sadly I can't get them these days, the drs frown upon handing them out cos theyre highly addictive.