Why is it that when i sit up in my bed, after a while when i stand up my left hip or pelvis area hurts really bad?

Please clarify: Where is the "hip" pain? On the side of the leg or in your groin? You list spinal fusion in your procedures. Is that a recent surgery? Do you have other orthopedic issues? More information would help to better answer your question.

Hip pain: The most common cause of hip pain is osteoarthritis of the hip joint. You may have hip arthritis if: the pain is in your groin, discomfort comes and goes, becoming more frequent over time, pain worsens with standing, walking and activity, and is relieved by rest, you feel stiff, you walk with a limp.

Muscloskeletal pain: Does the pain stay all day or go away? Medical conditions? Have you tried anything? Likely musculoskeletal. If you are not allergic and have normal kidneys you can try some motrin 200 mg, warm soak, massage, kinesiotape, and see if that helps. If you had back surgery , there is anatomical change which makes back issues more likely. If it persists >3 -5 days would seek medical attention