I also remember starting wanking at 7, in fact I can remember the very first time,I was in bed just rubbing but continued for longer than usual when suddenly this flood of warm exciting feeling started filling my groin and tops of legs, I was so taken aback that I did it again and again, 5 times in all, and all in the space of 2-3 minutes. (Oh how I wish to emulate this today!) I think I only stopped through exhaustion!
The orgasm I experienced back then was somewhat more pleasurable than the ones since puberty!