If I had atrial fibrillation would it have shown up on my ekg and stress tests?

Depends. It depends if you have Afib all the time or intermittently. Would only show up on EKG and stress tests IF it was present at the time. If you have intermittent Afib there are simple tests that can show how often it is present and how Kong it lasts. Some people can always or sometimes feel it's presence, while others are totally unaware of when it occurs.