Thought I'd just chime in here - I rarely touch chems thesedays, but occasionally temptation gets the better of me..
Regarding the leg pain after MDMA, I had exactly the same thing last week, and it lasted for about 2 days then gradually got better - I'm fine now. Never had anything like it before, extremely strange, and quite worrying.
I researched a fair bit and initially came to the conclusion it could have been something to do with age (I'm 43) and the amount of alcohol I had consumed the same weekend - although to be fair, was probably only around 5 pints throughout a day, hardly extreme. Alcohol is known to cause muscle aches in large amounts, particularly in serious alcoholics, a condition known as alcoholic neuropathy as I recall - with that said, I'm far from an alcoholic and only drink a couple of times a month, so certainly a bit strange if it was that.
Anyway, here's the kicker - I had 3 mates that did the exact same pills that weekend and on the comedown they all had this bizarre leg pain - quite intense pain in both front upper leg muscles - very weird indeed.
So, that lead me to the conclusion there might be a sketchy batch of MDMA/pills going round - or possibly something to do with having alcohol in our system at the same time - never had anything like that with using both before though, so that would be unusual too - with that said, there's little point mixing booze with MDMA, so not something I'd recommend, and of course it can add to the dehydration too, so best avoided!
I'm not 100% sure what these particular pills were called, but they were pink, and a quite big irregular shape - so be on the lookout. We only did about two thirds of a pill each and the high was really good, but clearly something's not right when four of us end up in the same boat on the comedown. God knows how bad the pain could have been had we done more!