Head shape

Has anyone had any experience with LO needing a helmet?? My son has torticolis (stiff neck) that causes him to look to one side and it has caused a large flat spot on the opposite side. He spends most of his time on his tummy now and we have been doing physical therapy to correct the toricolis. But I am concerned with his head shape, it is not evening out. And yes I have discussed this with his doctor and they just keep telling me we have until nine months to correct it, he is five months and I have been been asking about it since he was three months. I would think the sooner it is corrected the easier it will go. Just looking for some guidance or similar stories.....