Hi A..
When my son was 12 weeks old, I noticed his head was starting to get misshapen. I mentioned it to his pediatrician and his response was not to worry about it! AAUGH....Big mistake. 8 weeks later it was worse. I finally changed pediatricians and they immediately sent him for a helmet. Fortunately he didn;t have torticollis also. By the time we finally got the appt and had him fitted and then waited on the helmet, his head was getting pretty bad. The 2nd pediatrician told me that he should have had the helmet on by 6 months. If they don't get it on by a certain age, the results aren't as good. My son't head is not perfectly round but is sooooo much better than what it started out being. Now that his hair has thickened up, you can't even tell it.
Without the helmet, their facial features can get distorted, they can have eye problems. So it's not just about the "looks", it is something that you need to read up on and be on top of.
Some tips to help them get off that flat side.
Of course one of those wedges but what helped for me was moving his crib away from his wall. When they sleep next to a wall, they tend to turn toward it.
Or you could out his head down where his feet usually are (in the bed)
A mobile helps. I like the ones that were battery operated with a remote that way you can turn it on without going into the room.
The main helping tip....Tummy time. My son loathed tummy time. As yours get a little older, he will like tummy time more and more. Put him on his tummy and put some toy in front of him. Get him more interested in being upright than laying down (when not asleep)
Good luck and don't be upset if yours does have to wear a helmet, it isn't really that bad. I think it was definately worse on us than it was on our son.