I'm 18 and i have bad pain in my lower back, hips and knees when lying or sitting.cautionary test for arthritis came back normal. what do i do?:(

Musculoskeletal pain: 18y fem w. psoriasis: "back, hip, leg pain when seated/lying; not arthritis". These positions elevate biomechanical forces on pelvic girdle; imposed between upper body weight & ground force of seat/lying surface. Unstable pelvis joints from injury, MVA, childbirth, falls or Inherited Hypermobility Syndrome can torque & stretch large ligaments arousing generous "back & hip pain" & sciatica to knee.