I've obviously thought a lot about this. I think it all starts with Lyme, that crashed my immune system, and then the CFS viruses (HHV6 and EBV) infected my heart.
I think I was bit as a kid, probably after my first bout of chick pox, but before my second. You'll see in my preliminary results blog (that I just posted) they measured I have a really high pain threshold. I always had knee problems, and was sore but chaulked it up to athletics. Looking back I pushed through a lot, especially in my running days. But I just think my pain threshold kept me numb enough to it to think all's normal. But I had a bucketload of symptoms all my life - swollen lymph nodes, constant sinus infections, ear infections, nerve pain in my legs, chest pain, heart racing, extreme HR's during exertion, v low BP, seeing stars when I got up. I just didn't know any diferent... until I crashed at 30.