Not Feeling Well

I have not been been feeling well for the past 3 days. Kind of nauseous and headaches. Tuesday I still had a pretty good workout, but felt pretty awful for the rest of the day. Yesterday I didn't exercise at all and felt ok. Today I went to the gym and did all my weights and walked for 20 minutes. I feel very lazy and want to feel better and get back to my full exercising. Tomorrow.