Pain on walking

Hi everyone. I am new here! Only formally diagnosed yesterday, after at least 7 years of being dismissed.

I am laid wide awake uncomfortable in bed and questioning my diagnosis already. My stiffness has become worse very quickly and driving to work or standing up for a while is very painful (I have a list as long as my arm really which could be related or unrelated). I was diagnosed based on symptoms and SIJ inflammation on MRI. All blood work normal. Awaiting MRI of neck due to reduced range of movement.

Two things which are throwing me which don't fit:
Laying on my back with my knees straight exacerbate the pain and
I get pain if I am walking slow. So much so that I have to force myself into a hunched position, which is very painful and spasm-y, then relieves pain temporarily.

Does anyone else get this pain when walking? Its usually when walking slow/dordeling with kids. Not as bad if get a proper walk going!