I've been experiencing lower back pain for almost 3 weeks & i also get sharp pain on the side of my back in the middle & sometimes it hurts to move??

Rest, heat, medicine: Back mechanical problems can cause this. These are sprain , strain, etc. Rest , heat application, or alternate heat and ice will help. You can also use Ibuprofen, naproxen for pain and inflammation. Once the pain is gone, regular exercises to keep back muscles in shape can reduce the frequency of the problem. Use your legs and don't bend down if you have to lift or pick upanything