I Have For The Last Year Had Symptoms Of Unknown

I have for the last year had symptoms of unknown origin which my previous doctor just kept saying was anxiety although I knew it was not. I get flushing of the skin, followed by chills and clammy skin, painful tingling in hands and feet, a pounding heartbeat which many times keeps me up, restlessness and irritability, insomnia, skin twitches, severe nausea as well as losing 140+ lbs in 6 months despite eating the same. I am now down to 138 lbs at 5'10". I got in to see a new doctor and he listened and did bloodwork and everything aside from a enzyme called ALT and B12 were very low. These symptoms have gotten worse and more frequent and I simply dont know where to go from here since my family thought it was hyperthyroidism. My sister has it but my tests showed up normal. Any advice as to what to do? I am going to see cardio & gastro specialists this week but any advice would be appreciated. It's very uncomfortable and honestly quite scary.