I'm 22 years old, and over the past 2-3 years, I've noticed my body becoming weaker, with increasing joint pain under strain—something I never experienced before. I initially dismissed it as a diet issue, but the pain has worsened. When I grip something tightly or lift even moderately heavy objects, my finger joints hurt severely and often remain stuck in a closed position for a while. I have to slowly straighten them out, and if the pain is intense, I apply ice or wait for it to subside. My hands tremble when holding a pen or a cup, especially when I'm anxious or stressed. I don't drink or smoke. I also have significant pain in my knees and feet. My toes frequently cramp up, becoming immobile and causing intense pain. This used to happen mainly during sports or swimming, but now it can occur even while sitting or when I try to walk suddenly. What tests should I undergo to understand what's wrong with me, and which specialist should I consult for proper treatment?