Why does my body feel hot?!?

I've been working out (weights) this past week, and have been taking my protein shake 2-3 times a day, along with drinking lots of water. My protien shake contains 50g of protein, 124g carbs, 800+ calories, and 3g of creatine. I'm trying to gain weight, and have gained about 4lbs this week. I also take a seperate creatine pill which contains 2.5g of creatine hydrochloride. But i've been feeling kinda hot at times, and sometimes get headaches everyday or every other day. My muscles are really sore, but is that why my body feels hot at times?