fatigue from exercise -early symptom

I am 6w3d and man oh man am I feeling it now. I'm not generally super tired but I am an aggressive exerciser, and I have backed off quite a bit from my normal routine. Even the modifications I've made - it is getting so much harder to get through!!! I can't believe  it. This morning I went on an "easy" hike and thought I wasn't gong to make it! Otherwise I would say I don't notice a lot of change but this I certainly notice. Anyone else????