Any reason why my temperature has been elevated for 3 weeks?

You really don't have much of an elevated temperature, and since you are not feeling ill, it's just not a big deal. Higher temperature is not an enemy, it's a first line body defense against invaders. Most likely you may have a mild viral infection, and the slightly elevated temperature is one way the body can keep viral numbers in check while the immune system tracks them down for the kill. Body cells work just fine in a higher temperature, virus and bacteria do not. Without symptoms, it would be nearly impossible to figure out where the trouble is, and at any rate since you are not sick, there's no need to. Trust your body works, and just continue to lead life as usual. Until and unless there is something to bother you, you just don't have a problem.

i have no idea.... its prob nothing serious but u should go to the doctore to get it checked out just in case