Usually a rate above 140-ish is going to be flutter. AF can be between about 140 all the way down to 80, if you can believe it, but a proper 12 lead ECG is needed to determine so.

IF this happens increasingly more often, and I'm afraid the research suggests it is highly likely in all patients (AF is a progressive disorder pretty much always), you might wish to acquire a modern smart watch that can produce a rudimentary ECG. If there is AF going on, your watch will detect it. Then, you can download the record and paste it into your files and attach it to an email or an SMS to your cardiologist.

It is good that you self-revert before long. This means you're still in the paroxysmal stage of AF. It can last years. I got about four out of mine before the frequency and duration began to climb and I needed the intervention of a highly skilled, highly experienced, and very busy electrophysiologist (EP). The wisdom in the field is that you want to get control, either with medicine or with catheter ablation, while still in the earliest stage, that being paroxysmal. It becomes increasingly hard to win the battles as one progresses to persistent, and finally to permanent, AF. So my advice is to see at least a cardiologist now, and to ask about NOAC's (Novel Oral anticoagulants) to keep your risk of stroke low. What people forget, or never learn, is that a stroke from an arrhythmia, particularly AF, is high for even weeks after even a short episode. The reason is that a clot can form in the left atrial appendage and get dislodged some time after it has formed. When it gets pumped out of the atrium, into your left ventricle, and then into the left arterial descending (LAD), or into your brain................