It sounds like you have the pattern in hand, is this correct? What part of the sweater do you have done and what is the general construction of the sweater? Is it made in pieces that need to be sewn together, is it top down and other things like that regarding the way it is made? Is part of it still sitting on a needle? Counting the stitches you started with may tell you which size you were making. Counting the stitches where you are may help you determine which line of the pattern you were on.