Talk to Internal Medicine on Legs Knee Pain, Lower Back Pain

I am 34years old and I have two kid years and 4years My legs hurt alot especially when I lie down in the bed at night. When I wake up, I can't put my legs on the floor because my ankles hurt alot in the morning.. Nowadays, when I sit on the floor while bending my knees and then stand I can't stand because my knees are hurting alot.... My tests are cleared , vit d, cal, thyroid , cbc, etc etc. Eberything is in the range but why my legs hurts alot?