How hard should I push my doctor?

30F. I’ve had a a change in my health. I’ve had pain on my iliac crest area for months and my very lower back (literally right above my buttocks) for years, but I’ve chalked those up to being out of shape and having poor posture. What finally brought me to the doctor was the start of major brain fog and hand clumsiness. I constantly can’t think of words and I drop everything my hands touch which is new for me. She did an MRI for MS which came back normal, and she did an Xray on my right hip which was normal. Now I’m having bad knee stiffness and pain, especially when I get up after sitting for a long time. We did find I have low vitamin D so I am taking a prescription level vitamin D. I feel like ankylosing spondylitis could be a possibility for me but I’m terrified she’s going to think I’m diagnosis shopping. I’m just in pain!! She seems unconcerned and gave me a referral to a PT for my iliac crest area. My normal blood work was fine but she didn’t test any sort of inflammation markers or anything. Any advice??