5-year old herman tortoise

im not sure if my tortoise is hibernating or has died..... he's not shown any signs of hibernating in previous year i put this down to the fact that he lives in the house and it's always really warm. recently he's move to the opposite end of his tank away from the heat lamp, he hasn't eaten anything for about 4 weeks, he's not moving at all when i pick him up not even if i touch his legs which normally he would pull them into his shell. and hes starting to smell abit not alot like you would expect a dead animal to but there is a little wiff. do you think he is just hibernating or has he died???? please help.