What Causes Fatigue Along With Nausea And Headache?

I was working for hours in very hot weather. Around 3pm, after 8 hours of work, in witch 3-4 were in very hot weather, I became much more fatigued than normal, had a slight headache and nausea. I work another 3 hours to finish the work day. My skin felt very sensitive and sore like to the touch and the nausea did not go away and joints and muscles felt sore. I just thought I was getting sick from virus, etc. When I went to bed I had a spell come over me of felling very cold like I was submerged in ice. I got under blanket and started to feel better and fell asleep. It hit me in my sleep that is was probably heat exhaustion.