Side effects of exercise? The range of motion in my arm has become limited

It seems that muscles and fat have accumulated around my shoulders and back, causing my arm's range of motion to become limited. While having a larger upper body is beneficial, now when I sleep and lie on my side, my shoulders hurt. Perhaps it's due to increased pressure and weight...

Unbeknownst to me, the thickness of my arms has significantly increased. However, with a significant increase in body fat, I am once again increasing the proportion of cardiovascular exercise. I must challenge myself to reach 15% again!