Sinus Tachycardia and full exhaustion 24/7

I have sinus tachy since dec last year and still waiting for meds...
since then, however each and every day at work (very busy office/pwk/phones/pc) makes it nearly impossible to actually work-I feel exhausted from just sitting down doing nothing let alone walking around and doing stuff. i only feel relaxed once Im laying down watching tv on the couch. Sitting up my heart rate is usually around 100-120bpm....Am I crazy to have all these werid feelings...my muscles feel as though I have been working out and the next day there sore-that feeling in them....When I eat food its fast-when I stand too long (usually more than a minute atm) it races-Im so over being sick-
I had vertigo for a full week as well a few weeks back then an unknown body rash for 2 days but hospital said nothing about it
Does anyone else know what else I can do- The doctors just say-wait for the results-thats ages away I cant deal with feeling this low of energy and feelings to do stuff. I feel like im not even with it most of the day and my eys get strained and sore looking at a pc all day i just want to go home....I always wonder if something else is wrong with me so when I go back to the Hospital for results Im guna see if I can get an MRI or scan of some sort to make sure Its just my heart rate going fast for no reason......