1) Did you test it? (e.g. Marquis test)
2) Are you taking any medication? MAOIs and SSRIs will both affect your response to mdma
3) 0.5 g = 500 mg is a colossal dose of mdma. No wonder you were floored.
A normal dose is 0.01 g = 100 mg
Have a look at the Bluelight forum and particularly the stickies at the top of the MDMA page.
There is also a complete MDMA FAQ and numerous user experiences. Check it out.
Finally there are just some people who don't seem to have the usual response to MDMA , perhaps you are one of these.
Are you on any kind of medication at all?
Vitamins have a negligible impact on the effects of mdma
for the rest see this link: http://www.bluelight.ru/vb/threads/657228-Six-Simple-Rules-To-MDMA
It's like all drugs. We all react different to it. You may be less receptive, you may be in the wrong mood for it, the dosage may be wrong or it may not be Mdma but a substitute.
Are you sure it's MDMA? Well the thing is it doesn't exactly make you happy but it makes everything a lot better so if you do things that make you happy it makes them heaps better, so try dancing, hugging, giving or receiving a massage, having a D&M, having sex...
It does affect people differently. Next time try taking some 5-htp or tryptophan with it, see if that makes a difference. Do you have ADHD by any chance?
I have a degree in Psychology :) If you haven't heard about 5-HTP I really recommend it. Seratonin (5-HT) is converted from 5-HTP, which is converted from tryptophan, which is an amino acid found in many foods. That's why people will often recommend certain foods before bed to help sleep eg milk. People with mood disorders often have problems with their seratonin. As for ADHD I just know anecdotally that people with it are often affected very differently by certain drugs. Well actually dexamphetamines are prescribed for ADHD so there's definitely a problem with the dopamine right there. Personally I find MDMA doesn't make me want to dance or give me energy, I love sitting and chatting to people when I'm on it. And getting and giving massages! It makes me feel so much love. My fave drug. Shame it's hard to get good stuff and these days the pills in Australia often have meth in them which is not a very nice drug...
Well that sucks