Your neck needs a lot of support, and if you sleep on your stomach, then it can end up in an unnatural position which will cause aches, pains, and even headaches. Pillows need to be thin enough that they don’t angle the neck upwards. If the pillow is too thick, then you may turn your head to the side or bend it, which can cause pain down the whole length of your spine. Pillows shouldn’t be too thin, though, so as to not provide any support. All of the pillows on our list are at the optimal thickness for stomach sleeping.