No energy

Anyone else struggling with no energy?  I'm usually such an active person and lately it takes everything just to get out of bed and brush my teeth. I use to do 1.5-3 hours at the gym a day now I can't find the energy to do more than like a half hour walk every other day. I find when I push myself and have no energy that's when I get nauseous. I know it's healthy to workout and I miss exercising. But even beyond that getting up and going to work takes so much energy that I've become a flake on all my nighttime plans. Any advice?