Back pain causing breathing struggles

Does anyone get back pain and stiffness when standing for so long that they struggle with breathing? My back feels like it locks up and I need my partner to help stretch and crack my back to be able to get a full breath, especially at times when I've been standing over the hob/cooker sorting out dinner, it gets really bad. I want to cry from the pain and the stress of needing to take shallow breaths when this happens.

Also looking for a vent so apologies if this gets lengthy as I tend to waffle. But if this is something people can experience due to hypermobility, what is your experience when going through doctors/gp for help? I am currently on my journey through the NHS (I'm from the UK) and this year was when I realised that my experiences aren't what people deal with every day. Pains and discomfort are so normal to me, that I believed when people complained about standing too long in a queue or over a counter, that they also were experiencing severe back pain, knee and hip discomfort and hiding their tears for what they feel. I felt I was being weak and emotional but since discovering hypermobility and hEDS symptoms I've discussed with those around me and turns out they don't feel this way. I've been refered to a rheumatologist that dismissed hEDS as I don't show the mafans type symptoms, so diagnosed hypermobility and fibromyalgia. I have follow up appointments (not until next summer annoyingly), so am trying to document any struggles related to my hypermobility to express my actual experiences. Ive recently started to question if this breathing struggle and severe stiffness/locking sensation in my back and struggling to breathe when standing up working on something over a desk/counter is toes to hypermobility. So does anyone else experience this same issue? Any mentions of similar experiences or advice on how to help and avoid this would be greatly appreciated.