Which tests should I have for a psoriatic arthritis diagnosis?

I have a recent diagnosis of PsA. Systemic bloodwork is negative for inflammation.
My mother had lupus discoid. I have an inflammatory bowel disease that started around 2 years ago became disabling. I have psoriasis on elbows and scalp blisters/lesions that form scabs and are painful. My doctor has repeatedly tested me for rheumatoid factor and always negative. My joint pain started in my ankles and moved to my knees and hips. It feels like I have pain in my bones, too. I am often awakened by pain in these joints and experiencing intense lower back pain and newer pain in elbows.

What tests should I have? I am concerned as symptoms are hardly manageable and the combination of gastrointestinal and joint symptoms are becoming unbearable. From everything I am reading joints can become compromised and deformed permanently and I am worried as it seems my joints are rapidly worsening. I am especially concerned about my back and wonder what type of imaging should be done. Also, since my rheumatoid factor was negative my doctor canceled the referral to the rheumatologist that was suggested by my gastroenterologist and has me seeing a dermatologist instead. I have had issues with sleep and diagnosed with narcolepsy/idiopathic hypersomnia and the fatigue is so bad and the tiredness I can’t drive without medication.