I developed spells of brain fog, dizziness, blurred vision, extreme tiredness, etc out of the blue around age 31 (two years ago). After lots and lots of reading online, I was able to finally diagnose myself with hypoglycemia. Basically, eating three big, carb-filled meals a day was sending my blood sugar levels through the roof and back down through the ground. My family doctor was very little help (he wanted to subscribe scripts and nothing else) so I searched around for a specialist. I started seeing a doctor in a diabetes clinic and he set me on the path to healthy eating and living. At first, I did try a few of the medications on the market, but none seemed to make much difference and I was never comfortable with the idea of taking a drug everyday for the rest of my life. I've found that through eating/exercise I can control the spells about 95% of the time now. I eat very few carbs, lots of protein/fat and space out my meals throughout the day (I eat about six times a day).
Find a doctor you can trust, have your thyroid checked. Get checked for sleep apnea and depression. All of these things can cause what you are feeling. If none of those turn up any answers, start looking at blood sugar control. You can get a 5-hour glucose tolerance test to see how your body reacts to glucose.
I know you have been eating primal for a few months now, but I was eating (semi) low-carb after I first starting getting spells as well. I really had to ratchet down my routine, find foods that my body agreed with and get on a set eating schedule before I started seeing real, consistent results.