Hi lallim,
I’m not sure how long you slept on your mattress without the topper but it can take a few weeks for any new mattress to break in and for your body to get used to a new sleeping system that is different from what it was used to so it’s usually a good idea to wait for 30 days or so before making any changes to your mattress or adding a topper (see post #3 here).
If you are still experiencing any “symptoms” after that then there is more detailed information about the most common symptoms that people may experience when they sleep on a mattress and the most likely (although not the only) reasons for them in post #2 here.
There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.
These posts are the “tools” that can help with the analysis, detective work, or trial and error that may be necessary to help you learn your body’s language and “translate” what your body is trying to tell you so you can make the types of changes or additions to your mattress that have the best chance of reducing or eliminating any “symptoms” you are experiencing.
One of the most common causes of upper body symptoms is the thickness/softness of your pillow so you may need to experiment with your pillow thickness. This can be particularly challenging if you are a combination stomach/side sleeper because these sleeping positions are opposites relative to the type of sleeping surface that they do best with and a mattress that works well for one will often cause pain or discomfort for the other. It may be worthwhile considering reducing or eliminating the time you spend sleeping on your stomach because it is much harder on the body and can certainly cause a lot of issues over time both with lower back pain and with upper body and neck pain.
I would also guess that you may also have added too much thickness/softness to your mattress by adding 3" of soft latex to the 4" of soft latex that was already in the comfort layers (assuming that the 19 ILD was correct) … especially for your stomach sleeping … so it’s also very possible that you would do better with a thinner topper.
Phoenix