Reddit mentions of NEW Baby Infant Head Rest Support Cotton Pillow Memory Foam Prevent Flat Blue

Ok, a few thoughts:

My son has pretty bad reflux and is now on liquid prevacid for it. Is your doctor willing to explore this option? The meds helped my son immensely--it was like feeding an entirely different baby.

Elevate the pack n play to about 30 degrees if you can. Put some books underneath one end. Or, get a wedge pillow and slip it under the sheet. This is what we use for our kiddo and it helps.

Keep your son elevated for about 30 minutes after each feed if you can, to help with the reflux. Spit up is normal as the esophagus and digestive system is immature, but reflux is a bit different. It peaks around four months so expect worse before it gets better.

As for flat spots, it is a relatively new thing because babies are now on their backs vs tummies, so your MIL can shut up. Any time not on their backs counts as tummy time. They can even do tummy time on your chest if being on their actual tummy is awful. That said, do as much as you can on the floor to build up neck strength. If it's only for five minutes and it's five times a day, that's still good. It doesn't need to be for long periods of time. My son hated TT for a looooong time, and I had to persist in putting him on his tummy for short bursts multiple times a day. He's great with it now. Some babies don't like it much, and it just takes time for them to adjust.

If your son prefers sleeping on one side of his head or the other, or sleeping straight on the back of his head, try to alternate sides when you put him down. Move toys or things of interest to the side you want him looking to. It can be a pain in the ass but it does help. Try not to use the bouncer as it doesn't provide them the support they need, especially if his neck isn't completely stable. It is a suffocation hazard. The rock 'n play is just fine for naps if you can keep using that, or the PNP if you can elevate it.

Most kids have some kind of flat spot. Your son's may be a result of many things, including tight neck muscles. If you feel like he looks better one direction, massage his neck on both sides and gently tilt his head to one side for five seconds then the other for five seconds, about 10 times each, once or twice a day.

Lastly, a helmet should be a last resort after exhausting all other options. There have been recent studies that show that the "fixing" from helmets is almost purely cosmetic and doesn't actually fix the flat spot better than time would have and does in most cases. Also, helmets are thousands of dollars and have to be worn 23 hours a day. It should be a last resort.

Edited to add: our pediatrician recommended a specific pillow meant to help combat flat spots. It was an adjustment for little man, but it helped a lot.