1.First of all I need to know what investigation you had in medical check up.
2.occasional missing beat can be a transient and normal phenomenon. Bout need to be investigated.
3.The symptoms you had seems vasovagal or may be you overreacted.
4.As I said earlier we need to do investigation to rule out the underlying cause if any of the episodes of symptoms you mentioned.
5.I suggest 24 hors Holter monitoring of heart along with ultrasound
6.some blood test
as well like, full blood count, thyroid
function test, urea and electrolytes ,calcium and magnesium