I apologize for that I don't have time to read all the replys, but thats my 2 cents to what OP wrote:
First of all I feel sorry for you mate. I've been there, so I'd say yeah, it's normal for MDMA, if you take too much drugs.
Few things:
I think you might have took a little bit too much MDMA, such a strong dosage after not taking it for long time can give you a very intense experience, especially on a brain that is already not a "fresh-never took drugs sort of brain".
Such dosage may be too intense for your brain/cardiovascular system, so anxiety might be building up on a body already, transferring into anxiety in psyche.
THEN you did cannabis which often increase bodyload, heartrate, induce paranoia and deepen the experience... cannabis is known to go into strong interaction with other drugs so it went into some form of a bad trip, because things were already kinda out of hand and adding cannabis only deepened the problem.
Also melatonin from my experience can do things like MDMA - give feeling of anasthesia etc., so you pretty much did 3 substances that can deepen this "fleeting body-fleeting mind" experience, so to quote the classic: "you took too much man, you took too much".
I think generally mixing and psychedelic or MDMA with cannabis is risky, it can be very rewarding if you hit the point, but will make one feel utterly bad when it goes bad way or simply overload the psychophysical organism.
Next time if I were you I would took a little bit less MDMA. And if things go bad: never add cannabis but wait! Same with melatonin. Also if you plan to mix MDMA with Cannabis (which is great mix if done right), just take even less MDMA in the first place. That's my observations on this topic.
I think "healing" drug problems with other drugs is very risky. I think best solution is just wait for everything to settle to don't deepen the problem.
Thats just my opinion thou after a few "you took too much man" I did myself.
Take care and wish you better trips in future