You may want to read this: http://perfecthealthdiet.com/2011/08/carbohydrates-and-the-thyroid/

There is evidence that in some people lack of glucose can cause reduced T3 (thyroid hormone) production and the symptoms you are describing. Your body reduces T3 production in order to spare the use of glucose so your brain will have enough.

This proved to be true for me. I am hypothyroid and I've found I need about 80 gms of starch carbohydrates /day to feel proper. Otherwise my T3 falls and my TSH rises even with T4 supplementation. Vegetable based carbs do not seem to help much for me. According to the same website I referenced, veggie carbs are largely digested by gut flora and provide very little actual glucose. Starches such as white rice or potato are recommended.

Perhaps you are sensitive to the same thing. I added starch to my diet and not only felt better, but continued to lose weight as well.

Good luck finding your solution.

Paleo is not LC or VLC, it is eating real, whole foods. I probably consume an average of 150g per day of carbs. I also found that if I got too low, I felt more lethargic, and my sex drive, which has always been high, began to drop. Throw in some sweet potato, butternut squash, or some fruit. Weight loss is about controlling your appetite by eating whole foods that leave you satisfied, and give you the energy to function. Experiment a little to find the right balance.

Being VLC makes you pee out a lot of your electrolytes so you need supplement more than you are probably used to. Try increasing your intake of sodium quite a bit (4-5grams) during the day and magnesium before you sleep.

Since going VLC I've had issues with lethargy and then the odd insomnia symptoms as well. I'm telling ya, the sodium really helped....as did the mag for sleeping.

Get some good quality kosher salt or Himalayan and use it liberally when you can and also get some bullion cubes and have a couple of those a day (about 900mg of sodium each).

I also use trace mineral drops that are low in sodium to make sure I'm getting enough mag and potassium etc.

I was in the EXACT same position as you a few weeks ago after being strict paleo with no fruit, >50 carbs per day, etc for six months. During that time I also lost 15 pounds at 5"1 (haha it's funny how similar our experiences have been) but had ZERO energy. I was weary of adding carbs because of all the negative comments about them from different sources, but adding some literally saved my life. Remember you don't have to eat 5 lbs of them to experience the benefits! Try just adding in one sweet potato, or in my case I eat some garbanzo beans (not paleo and some people can't tolerate them, it's an individual thing) but anyways I almost IMMEDIATELY felt like a million bucks after reintroducing those things. And my weight is still steady. The energy increase was AMAZING though. I felt like I could run a marathon after (a feeling I hadn't felt in MONTHS). I think I had actually FORGOTTEN what it was like to have energy, I tried just accepting that my low energy levels were normal or something. But seriously. Adding in just one starch a day (not from fruit.. which doesn't give me the same effect) but from starchy vegetables or beans, CHANGED MY LIFE.

If I picked one option, the other two would get jealous.

Anything from 20-150 is fine every day. Try to go over only once in a while.

Eat real food.

Try low carb in the beginning for the fastest fat loss then play around with them to see how you feel.

Congrats on the weight loss! The simple answer is this: you need more of something in your diet, either carbs or fat, or both. You could try adding some coconut oil to your coffee, or maybe start having 1/2 of a small sweet potato at dinner and see how you feel. If you don't have enough energy then something is missing from your diet