After a lot of tests, they said i have sinus tachycardia. resting heart rate has been 120+ for last 7 years. introvert, social anxiety, sedentary life style. can i workout? is it treatable? i can walk miles but breaks after 3-4 sets of stairs.

As a matter of fact: (my opinion only) EXERCISE properly SUPERVISED is the best TREATMENT for your condition! A well conditioned heart slows its rate! Exercise also decreases "nervousness" and when accompanied by a goal oriented program and a good instructor increases concentration!! ( Ask any athlete what I mean!!) Hope this helps and GOOD LUCK BE WELL! Dr Z

Stress testing: It seems like the easy answer would be to undergo cardiovascular assessment - the doctor will likely order a "stress test" to address your concerns.