This is the "lost magic" thread, to give you an idea of what you may be experiencing:
http://www.bluelight.ru/vb/threads/...!-quot-megathread?highlight=lost+magic+thread
I have to disagree that MDMA feeling "different" from when you first started is odd, or likely adulterated pills- this is aVERY common effect. It's typical for MDMA to have a development or "journey" for each individual- at one point, the drug that once made you extremely outgoing now makes you floored etc. There are lots of theories as to why, but usually the simplest one is that you've antagonized your 5-HT receptors to the point that they respond differently to this chemical, therefore not giving you the same feelings you would when your brain was new to MDMA.
My first 6 months of MDMA use, I (unknowingly) abused it and rolled every 1-2 weeks. I was certain we had taken a different drug altogether when all of a sudden MDMA made me feel floored, unable to proper string sentences together- I was still cuddly, and enjoyed light shows- but MDMA used to make me talk to everyone, dance all night, and the music sounded extremely amazing- I was quite confused. Getting a reagent test kit (
www.dancesafe.org) confirmed for me that I had MDxx pills, it was merely my brains reaction to the chemical that had changed.
I would research piperazine experiences, along with the many other adulterants (check out the directory in my signature). In general, if you are waiting the proper amount of time or longer (30 days is a minimum, but it's good to take even more time off than that every now and then) you should be capable of fulfilling MDMA experiences, but expecting any drug to work the "way it used to" will often leave you disappointed- and MDMA is probably the greatest example of that. Even for those who don't believe that "losing the magic" is a physiological scientifically "true" thing, the loss of magic can simply be due to the lack of novelty of the experience.
Regardless, do your research. Though it's not what you want to hear, it's quite possible MDMA is effecting you differently now. Acquiring a test kit is very important for your safety, and to figure out if it's you or the drugs.