30/f/overweight. no health conditions except anxiety. no family history of heart issues. suffering with pvcs/sinus arrhythmia. blood pressure/ekg/echo all normal. 200mg sertraline, 10mg buspirone, 2.5mg bisoprolol. will my heart stop? i'm scared?

PVCs and sinus arrhythmia are very common and do not result in heart stopping. If you have not had a thorough work up, it is possible to get a second opinion, but it sounds as though your doctor has been fairly thorough already. Perhaps a discussion with your doctor whether a referral for better control of your anxiety may be useful, if the doctor is comfortable with the heart rhythm. Good luck.