How much weight should I lose?????? ?

Im eleven and 347 pounds I am 5 feet tall I say I'm pretty fit I can at least get up ( but not walk) I was just woundering how much should I lose if any at all, i eat ice-cream and mcdonalds food products, I order 2 big macs with extra cheese 2 orders of large French fries 1 XL montuin dew and for dessert 2 hot fudge all for me but the most reason I asked this question is everybody (even my mom) calls to me and says " lose some weight fatty" my brother and sisters won't expand there door like I did so I can fit through once in awhile ( without going sidewise, sometimes I can't even fit the door that way)