When are palpitations dangerous? i've had over 100 ecg tests. 2x echo tests. 2x 24 hour holter monitor. all normal. dr says i only have ectopic beats. never had longer monitor. palpitations feel strong recently. can these kill me?

With that level of prior study all proving normal the issue is likely not your heart. Health focus is often a subconscious coverup for other things in life you haven't identified or dealt with. I would find a life coach/therapist, learn stress management & relaxation techniques and on the way you may discover some trigger issue you will then have the help & ability to deal with.