Why do we get dizzy when walking, because I also get this.
I've had most of the same symptoms for almost a year now and I was recently diagnosed with POTS. Although the only time I had an arrhythmia was a few months ago and only the ER nurse saw it before my heart started behaving again. The echo didn't see anything weird and the blood tests were normal.
I'm not as experienced with atrial fibrillation but the symptoms you mention belong to POTS for the most part.
Go see your cardiologist and if they dot have answers, get them to refer you to another. Getting an official diagnosis is important and one of the harder parts of POTS (or at least more annoying).
If you want to rule out POTS, take your heart rate after lying down for ten minutes then take your heart rate for ten minutes after you get up quickly. If the increase is greater than 30bmp, it's probably POTS. Otherwise, you can rule it out as a likely possibility. I hope that helps a little and don't give up!