May i use an antidepressant drug like amitryptiline for a short period and then just quit?

Won't help: Antidepressants take 2 or more weeks to start working. We then recommend continuing the med for at least 6 months (more if you have repeat episodes of depression), to decrease the risk of relapse upon stopping. So "short period" use probably won't help depression, and even if it did, the depression would likely come right back. Amitriptyline can be a short-term sleep aid, though.