How did you feel first few days on LCHF?

Sounds like you're experiencing what was once known as Atkins flu, following the popularity of the low-carb Atkins diet.
Bad news over. Good news - shouldn't last too much longer. It's harder for some than for others.That's how the dice roll
More details :

http://www.livestrong.com/article/381434-what-is-atkins-induction-flu/

Hope you're feeling better soon.

Geoff

I have copied this from the diet doctor site, I hope it helps

The most common side effect on low carb is what most people experience during the first week, often during days 2-4. The “induction flu”, so called as it can mimic flu-like symptoms.

Headache is very common during this period, as is feeling tired, lethargic and unmotivated. Nausea is also common. It’s also possible to experience confusion or “brain fog” – feeling not at all smart. Finally it’s common to feel irritable – perhaps most clearly experienced by the rest of your family.

The good news is that these symptoms usually disappear by themselves within a few days. The even-better news is that these symptoms can often be avoided altogether. The main cause is usually dehydration and/or salt deficiency, caused by a temporarily increased urination.

The Cure: Water & Salt
Any problems can be minimized and sometimes entirely cured by getting enough water and salt into your system.

For example try adding half a teaspoon of regular salt to a large glass of water. Drink it. This may reduce or eliminate side effects in 15-30 minutes. If so, this may be repeated once daily if needed during the first week.