Hi sweetie:
I had a friend who used to take X, and days later, she would fall into a horrible dark depression, feeling sad and crying for no reason. I read up on it a bit for her, and apparently your brain is depleted of serotonin after you've taken this drug.
It passes, so you probably just have to hang in there. Try doing things that make you feel happy; watch a funny movie, listen to your favorite music, go for a walk in the sunshine.
Good luck; I hope you feel better soon.
How much MDMA and how many days did you take it? Your symptoms are a little unusual after just one dose.