Have the test done, I was in a similar situation as yourself.
I had the nuclear test done and it showed my heart wasn't getting enough blood, I then had an Angiogram (Cardiac Cath) which showed two 90% blockages and one 70% blockage - I had a triple bypass 3 days later.
I'm not overweight, had good BP and good cholesterol numbers.
Family history is major risk factor of coronary artery disease and since your dad had a heart attack you could be at risk yourself.
Good Luck.