I'm surprised no one has mentioned chiropractic care. All three of my little ones saw a chiropractor shortly after they were born. It started when I noticed that my first wouldn't turn his head very easily to a certain side. I asked my chiropractor about it when I went in for my own adjustment (I slipped and fell down the stairs hitting my tailbone a few weeks before I was pregnant and had to deal with that discomfort throughout the pregnancy.) My chiropractor said that it's common for that to happen to babies who happen to be "stuck" in on position for a long time in utero. He figures that's what happened with my first.
The adjustments were so gentle (pressure you'd put on a tomato) and it took just a couple of visits and he was turn his head either way easily.
I took my second in because I figured he needed to be looked at as he was a very big baby (10 lbs 5 oz!) and I figured he had to have be squashed for some time! Again, just a few adjustments and he was fine.
I just took my littlest (she's six weeks) to see the chiropractor on Monday. It was just for a checkup, but I had noticed that whenever I ran my hand down her back she squirmed away. She was laying transverse in utero and when the dr. did the incision her hand popped out first, so he had to push it back in and manuever her around to get her out. (All three ended up as c-sections as I had complications with my first and a failed v-bac with my second). Her neck was out of alignment on one side and her lower back was out on the other side.
For those who question chiropractic on little ones, think about this- child birth is one of the most traumatic things your child will go through- getting squeezed through a birth canal or messed with during a c-section can do some harm. Every single chiropractor has told me that he's done adjustments/checked over his child shortly after birth.
And my little girl seems to be much more happy as a result of her adjustment. He said that because she was laying transverse it didn't give her body as much room if she had been laying up and down at the end, which is why her back was out.
It's an option for you to try and in the long run, possibly not as expensive as wearing the helmet etc.
Good luck!