Could you recommend a shop in eastern Switzerland where it is possible to test different sleeping pillows and to hear some recommendations from the experts (especially which of them might reduce neck pain by sleeping)?
One thing to consider (and obviously I am not an expert), is that the pillow that may ultimately cure your neck pain may be the one that is most uncomfortable for the five minutes that you test it for in the shop.
Conversely, the beautifully soft pillow that you sink into when you test it may be terrible for support to reduce neck pain.
Thirdly, what you do (or don't do) in the day may impact how well you sleep at night, and how much pain you experience at night.
I now absolutely swear by using a memory foam pillow. It's the right combination of firm so it relieves your neck muscles, but there is still a bit of give to make it comfortable. It's also the only material I've found that doesn't seem to degrade over time, I've had mine for ages and it doesn't seem to have changed its structural integrity at all. The only difficulty was finding one of the correct thickness, 1-2 cm can make a big difference! Also, it is less thick in the middle than at the edges so my neck stays straight.
I'm not sure if you'll see this* but magnesium oil is awesome for pains like that.
*I tried to leave that as a rep comment instead (so that you'd see it), but it wouldn't let me give you new rep again so soon.
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People could also look on amazon for pillows that are designed for alleviating neck pain, which probably depends on whether you're a side-sleeper or back-sleeper, etc. I know there are various neck-support pillows out there.
Also, I use to get awful neck and upper back pains and eventually realized that it was due to bruxism (grinding and clenching my teeth at night), which I wasn't even aware that I was doing until my dentist pointed it out.
At the beginning buckwheat seeds pillow was very hard for me and could not understand my husband loving it but now it is very comfortable. They sell in some pharmacies or also on amazon, relatively cheap below 50fr.
I have been using a millet seed pillow for years (Hirsenküsse), this proved to be only solution to my neck pains. After six months the pillow can be emptied into the green waste. At the moment I think they are only available on-line.