This maybe bad advice but I always find benzos and weak opiates help just to take the edge off a bit. Might help u feel a lillte better until your serotonin levels get back to normal. We've all been where you are trust me I've been suacidal for a week after a heavy weekend but u will get back to normal it just takes time. Be safe n be positive
Benzos+opiates seem like a miracle cure. Strong opiates work too.

Ofcourse they are a short term 'patch-up methods' and not a solution. While they'll mostly kill the hangover, as effie said, they're very habit forming drugs. (Even if you 'only' use them for stim comedowns, things might very well escalate from there.)
So I'll stick to suggesting isotonic drinks, vit C, magnesium, 5-htp, sleep, and healthy food before, during and after rolling. That's pretty much all I can think of right now.
I usually gobble up a multivit pill, a magnesium pill and drink loads of orange juice. I don't really pay attention to what I eat, but I make sure I eat enough.
As to the content, piperazine pills give me that kind of hangover. Mdma gives me a mild depressed feeling, nowhere near as intense as you described though.
/e: Oh, so you've figured out it's speed. Well, that tends to give me a bad hangover too. Especially when the two are combined. Nowhere near suicidal, but pretty damn shitty nonetheless. Overuse caused this for me aswell.