Thanks for your question on Health Care Magic.
I can understand your concern.
No need to worry for cardiac diseases because your multiple ecg s are normal.
Possibility of involuntary muscular contractions is more in your case.
Common causes for this are low calcium and magnesium level.
So get done serum calcium and magnesium level.
If deficiency than you need supplements.
If both are normal than sometimes
stress and
anxiety can also cause fluttering sensation in chest.
So avoid stress and tension. Be relax and calm.
Don't worry, you will be alright.
First rule out calcium and
magnesium deficiency.
Hope I have solved your query.
Wish you good health. Thanks.