Hi mobin.
Welcome to our Mattress Forum. 
While it’s not possible to “diagnose” mattress comfort issues on a forum with any certainty because they can be very complex and there are too many unique unknowns, variables, and complexities involved that can affect how each person sleeps on a mattress in terms of “comfort”, firmness, and PPP or any “symptoms” they experience … there is more 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 that you may find informative.
In some of your pictures, your spine trends upward, in others it’s quite aligned, and in yet others it sinks downward - which to me points to a pillow problem. Upper back issues can point to a pillow that is either too high or too low for your body type or sleeping position and doesn’t maintain the gap between your head and the mattress and keep your head and neck if good alignment over the course of the night which can affect the upper back as well.
Post #2 here also has some other suggestions that would be worth investigating.
NikkiTMU