If you are not able to go to the doctor soon to get weighed (which should be free if you just walk into your regular doctors office and ask to be weighed but nothing else) then maybe you could consider a new scale?
This one is available on Amazon and the reviews are fantastic.
http://www.amazon.com/EatSmart-Preci...769250&sr=1-18 It weighs up to 440lb so if you really do weigh that much, it will tell you. It only costs about $35 and offers free shipping.
It's important to only weigh on a hard, level surface with a home scale so avoid the carpet