If you can't detect an irregular heart beat... ongoing for more than a minute or two, I'd say you do not have AFIb. By the way, treated, AFib is not life threatening. Any heart aliment increases the risk of more serious heart problems, but most are not in themselves life threatening.
Is you resting HR higher than before the "weird" feeling"? On affect of AFib is an increase in the average heart rate measured of a minute or two, longer if you like counting.