hi there i had a very simular situation to you, with a pup i`ve bread, simular breeding started at a 1 years old tryed every thing, been to vets lots of times tryed all sorts of diets every thing. i was told by the vet that is was brought on by her coming in and out of seasons and been immature! i was given the oppertunity to have her neuted or cope with it as she will grow out of it! and sure enough she has shes 3 & 1/2 now and been fine for a few years (touch wood!) hope this helps a little!