Be patient - this will pass.
We, as breeders, often get questions from first time Toy or Mini Aussie owners about the look or quality of the puppy they have purchased. The puppy uglies set in somewhere around 4 to 6 months and can last until they are 12 to 14 months old.
That chubby darling puppy you got at 8 to 12 weeks old all of a sudden looses most of it fuzzy hair, the legs grow way faster than anything else, the puppy gets really thin and the head shape doesn't look right. You begin to think that the breeder may have slipped one by you. Be patient - this will pass. Just as teenage humans go through that gangly uncoordinated stage, so does your puppy.
Notice that at 6 to 9 months they seem to grow taller at the hip than at the shoulder and then the shoulder will be higher than the hips. This will level out and they should end up with a even top line.