I suffered from this for a few years, where I really had to push myself to do basic things - It was like chronic fatigue. I had a burst of energy, went to the gym and found myself floundering after a few months.
I was burnt out, and had to take a step back for about 6mths. Started eating healthy food, drinking more water. You need to take it slow, take a step back. Maybe get the doctor to run some tests to make sure it isn't anything medical.