Flashback trip urgent help..

Withdrawal from what?
Fuck, if you're that worried why not take some time to research shit a little bit more on your own? Like what substances you've taken over the course of your lifetime do.
Or start asking some real questions.

 

death is a part of life, thank you for your sympathy.

if you suspect the event is the cause of your troubles, then not giving your Dr all the information is only hurting you. you cant get in trouble for something you did to yourself in the past.
if you are otherwise healthy, look at environmental changes. just started school again... cafeteria food? processed food? something that may have damaged your blood vessels? (you mentioned cold being a similarity of events)
if you used to be in sports and are not now, you may be pumping blood at a different rate, or getting oxygen out of the air with each breath. seriously, tell the doc all the information you can about the situation.

 

I say BS. But that's my opinion.