I have been very stressed and anxious lately due to specific events.now i feel constantly anxious even when not thinking about anything. why?

A few ideas: One theory could be that you unintentionally trained a behavioral habit, but that depends on how long and severely you were stressed for. Habits (good and bad ones) generally take at least 3 weeks to train. You can tell it's a habit because you'll do it and not have to think about doing it (like driving a car). Or maybe what you were stressed about never really resolved. Hope this helps