Meth today isnt like meth a decade ago. Its all made in huge batches in Mexico now.
This is all speculation based on a little knowledge. But, it used to be made in smaller batches using different reactions to get the meth. I think the word is racemic. Like, today's shit is more or less racemic than it used to be. It makes it a ton more psychologically harmful. Which is why you don't feel comfortable like you used too.
I understand what you mean. I can do a whole gram in a day now. That is insane. It isnt tolerance causing it either.
Anyway, I wish I had more details to give you other than its just not the same shit anymore. But, that is really what it boils down too.
Even more reason too leave the stuff alone, my guy.