does anyone here use Tretinoin? if yes can i just buy it like that or must i go to a dermatologist?

Depends on the country, I know where I am you need a prescription from a doctor/dermatologist.

What country are you in? If you're in Canada I can tell you how to get it online and it's delivered right to your doorstep. It's pricey but very convenient and the nurse practitioners respond fast.