Well I can only relate with caffeine, that just sounds like the drugs doing their thing lol (i wouldnt know because ive never taken those, and dont really plan on it)
Of course your brain is crashing, depleting you of your happy chemicals after use of such drugs, (i mean this forum is all about these sorts of drugs, i dont know all the details, and not trying to bash on anyone. sorry guys)
your body could just need sleep at that point, but the drugs are keeping you awake, or just crashing you so hard.
I always love my initial cup of coffee, or cup of black tea, but after a while, i do indeed feel shaky and weird. i do have a bit of anxiety as well. I at first feel focused and energized and happy. and after a while just strung out like a zombie, but still having a fast-paced mind, unable to sleep. Probably just need to sleep. Well caffeine can dehydrate you. and it can suppress your appetite (all uppers can) so you forget to eat, etc. its just a matter of taking care of your body, your mind, and your soul!
the more you expose yourself to socializing and whatever you're anxious about, the faster youll get over it. Go and meet new and better friends, maybe you aren't comfortable with the people you hang out with because you don't like them/they aren't your true friends. Exposure theory; face your fears! :D
but ill admit im a loner myself. but idc really, i always have the opportunity to meet new people (I live right outside a college, tons of ppl walking by my house all the time) but i guess i choose not to. or maybe im just lazy, im kinda fine the way i am now

but always could be better, but def could be worse!!