Hi, My first major sign was a near-faint (totally blacked out, couldn't hear anything) at the age of 13. For much of high-school, I was chronically fatigued and weak and experienced episodes of high HR and low BP. There were many symptoms that accompanied this. Some of them include: --Chest pain --Migraines --loss of sweating --lightheaded, dizzy, palpitations --excercise intolerance --heat intolerance --poor concentration at times --funny feeling in legs (and sometimes arms) ... like they are really heavy or something. --noise and light sensitivity --flushing --big pupils --tingling, cold It is difficult for me to remember what my very first symptoms were because I wasn't diagnosed until the aged of 17 --- quite awhile after my symptoms began. Also, I think that POTS can be cyclical in nature---I don't know if that is what you are experiencing.