You can have dysautonomia without having POTS - that's where I'm at! My heartrate doesn't spike enough to be a potsie but I still have debilitating symptoms like dizziness, fatigue, etc. I think the highest I've ever seen it at rest was around 90. Migraine and stomach stuff can also be dysautonomia related. I was diagnosed with orthostatic hypotension which is a less intense heartrate jump than POTS paired with low blood pressure. Have you monitored your BP before or just your heartrate? That may help explain your fainting/syncope