hi it sounds like ectopic beats to me too, do these beats feel heavy and slower than normal heart rate,i mean there is pause between the beats then there is a hard beat this is needed to push the blood through as there is more blood.
these are really nothing to worry about if the heart is structrually normal and has no electrical problems. Anyone experiencing these should always see a doctor to do and ecg, if the ecg doesnt catch anything ask for 24 hour holter monitor.
i have suffered anxiety too not long ago and i get them too and this anxiety will cause them to happen more, the more anxious you are the more you will get and feel, when you get one dont even think about them you will only make them worse just ignore them.
they will more than likely tell you its your anxiety and control that for you with meds, young fit and healthy people get them to even when they arent anxious.
good luck with the tests
More than likely you are experiencing some premature beats either from the ventricle or the atria. During a premature beat the heart pauses and compensates for the extra beat by resetting itself. During the longer pause between beats the ventricle fills with more blood than usual. This causes the next normal beat to be harder and stronger than normally. The ventricle must contract more violently to push the excess blood out of the chambers that has built up during the compensatory pause. More than likely it is a benign condition and nothing to worry about although premature beats can be a sign of some other possibly serious underlying condition. I would go to the doctor and ask for a 24 hour holter and echo cardio heart doplar just to be sure.