I am desperately trying to identify the cause of chronic pain in multiple joints.

[JL_1976]

Over the past 7 months, I have developed worsening pain in joints which started in the front of my hips and lower back. The pain has spread to back of hips and thoracic back region. I have intermittent pain in one of my left ribs, and left elbow. Pain in hips and back exacerbated by exercise but is also waking me up at night. pain worsened by sitting long periods. The pain is a 5 out of 10 but is always with me. Relevant facts about me:
1. 41 y.o. male in excellent physical condition at 151lbs 5 foot 7 in,  with workouts 5-6 days per week before onset of symptoms. Active in physical fitness for 20 years. Good blood pressure and cholesterol.
2. I was a light smoker for 10 years and by light smoker I mean 1-2 cigarettes per day. Pack history less than 3 years. I have no respiratory issues whatsoever.
3. legg-calve perthes disease right hip as child successfully treated.
4. No history of any chronic disease and no identified cancer in ancestry through cursory review.
5. healthy appetite and minor weight loss (5 lbs)
6. Extreme anxiety and panic attacks over symptoms and recently treated with prescribed meds which have helped with anxiety but not physical manifestations.
7. MRI of pelvis and lumbar indicate no issues with sacroiliac region, bilateral cam type impingement (FAI) and posterior impingement in hips. Mild tendonopathy in right gluteus medius.
8.MRI in #7 above detected abnormal diffuse bone marrow signal abnormality (low T1 signal) in visualized portions of spine which spared the femurs. heterogenous and non-specific. Subsequent Oncologist workup included physical exam and complete skeletal bone scan revealing only mild uptake in hips lumbar and AC joints indicative of mild degenerative change. No focal uptake. Hemo/Oncologist recommended no further testing.
9. MRI of right shoulder indicated early distal clavicular osteolysis in right shoulder and rotator cuff tendonopathy. Prescribed therapy yielded moderate relief but returned when I stopped therapy over concern of worsening symptoms in other joints listed herein.
10. Multiple CBC's throughout the process and urinalysis at my request indicate absolutely no measurements outside of ranges, aside from slightly low Vitamin D which has been corrected through supplementation.
11. Rheumatologist testing for AS biomarker negative and is of the opinion problems are of no auto-immune origin, nor are they osteoarthritis. Referral to Orthopedic surgeon.
12. Orthopedic surgeon appointment is forthcoming in 2 weeks to evaluate next steps in testing.
13. Slight nausea and sleepiness and headache i attribute to side effects of anxiety meds listed on the labels.
14. Do not believe this is psychosomatic as I am an otherwise happy, active, wealthy young man so blessed in my life.

I have no diagnosis- only constant pain. After visit to orthopedic I am considering requesting a bone marrow biopsy and multiple myeloma blood tests at my own expense in response to T1 signal abnormality described above.

My question: With this physical and medical history, what is most likely the cause of my pain? Please help me I am getting desperate as my quality of life is deteriorating.