Hairline fracture in foot???

I fell down the stairs, and hurt my foot badly i went in for Xrays and they didnt find anything my DR thought it was broken and suprized that it wasn't i have to go back in again to have re Xrays if the swelling doesn't go down. It is swolen and discolored but the strange thing is it is REALLY cold even up to my leg it is cold If i elevate it makes it worse and my foot just fells really weird... it gets numb alot, and more but how do i know if i have a hairline fracture or bad bruseing or a sprain or anything like that? It got hit really hard on the stairs probally just as hard as getting hit by a hammer, SO how do i know what it is, bad bruse, brake, sprain or anything like that please answer and help FAST i can't wait