Unexplained lightheadedness, everything is normal, at a loss.

(27y female) I am having several hour long dizzy/lightheaded spells, with increasing frequency, currently 1-2 times per day for about 2-3 hours. Will feel light headed, short of breath, pain in feet (some very minor swelling), cramps, headache, nausea, and I will be terribly out of it. Compression socks and raising my feet helps. Labs (CBC, thyroid, ferritin) were done: only thing of note was creatinine is just under normal range and TSH is at the very low end of normal. EKG normal . Blood pressure checked during episodes is about 110/70, which is higher than my normal. Not orthostatic. I check at home with same result. Pulse ox normal. Glucose checked during episode at the doctors, normal. No correlation with eating, salt, and caffeine. Worse when exercising or after hot showers. Not inner ear as I have had BPPV and this is different. I have had panic attacks/anxiety in the past but this is very well managed. I am vegetarian and struggle with pretty extreme pickiness at times. But I am quite healthy and do yoga and walks. The dizziness is getting worse and more frequent, I trip more and stumble. My doctor wants to do a one month follow up but this is misrable and it’s getting in the way of physical activity. I just want to know what is even left to check as my doctor suspects something malnourishment related but not what specifically. Plus during the worst of my episodes, it’s been very scary and if this continues to get worse I do not want to be injured falling or fainting.