My POTS symptoms started after a year of misdiagnosed Strep. I had fatigue as my first symptom, then sinus infections/allergies and GI issues. I've had tachycardia pretty much my whole life, but just didn't know it was abnormal. Four years ago, it started getting really bad when I was working a job where I had to stand for 10 hour shifts outside in 100* weather. I thought I was just having issues with low blood sugar and severe allergies. I always knew I had trouble standing for long periods of time (and I'd often shake uncontrollably while standing, but I just thought it was nerves or something) but I didn't attribute my symptoms to it. My doctors were suspecting Lupus or early MS and I kept testing negative for both, so I searched online for things that had similar symptoms to those disorders, and found some information about POTS. It totally shocked me when I first tried a poor man's tilt on myself and found that my hr increased by 60+ bpm!