For those with CFS and OI - did everything come at the same time or were you sick with other symptoms first and then OI appeared? I had many symptoms for years, but noticable tachycardia (diagnosed POTS) did not appear until several years in. I don't know if I developed POTS on top of CFS. Or is POTS is part of CFS. Or if it was always POTS and not CFS. Any input is appreciated.