I struggled with the same thing and wanted to give up. until my teacher said to start with the chin rest. I didnt want to spend money but gave in and just bought a new chin rest that is 35mm. It solved a lot of my problems, I bought a shoulder rest that I could bend to my comfort and adjustable height. Between the two and posture changes, I’m not hurting anymore and am enjoying playing now.
It was an investment of almost $75 but totally worth it. My playing even sounds better.