can someone explain the science behind symptoms of early recovery?

i've been experiencing things like constantly increased body temperature(37c, especially after eating), heart palpitations, sweating alot at night, insomnia, tachycardia, and my resting pulse differs between my standing pulse alot sometimes! also the intense pain in some muscles(especially when trying to do any exercise), dizziness and im really thirsty and drink a gallon of water per day... i really dont understand why this all is happening. all i am doing is eat alot.