I’m really sorry to hear of the struggles you’re having, and that you and your GP don’t seem to have the right relationship to get you the answers you need. There are some sensible suggestions here in terms of extended tests you could discuss with your GP, and undoubtedly there are times a bit of persistence can lead to picking up some rarer conditions. I really hope that together you are able to make a plan that you are content with as it’s no good either for you or (genuinely) your GP to feel trapped in this cycle of normal results but worsening symptoms.
It’s unbelievably common for people to reject what can be perceived as a dismissive response from their care providers when diagnoses such as anxiety are mentioned. Clearly I don’t know how that suggestion was put to you and can’t speak to whether it was done in a compassionate and supportive or a seemingly less caring manner. Nonetheless it is what your GP seems to be going with and honestly you lose nothing by giving any treatment options they’ve suggested a go. They will be a lot more inclined to perform investigations for rare conditions if you work with them and trial whatever therapy they are offering. If it doesn’t work after a reasonable period of time then you have essentially proved your point, and they will feel listened to. It might sound strange to put it that way since they are supposed to be listening to you right, but their job isn’t easy and this isn’t America, they are hugely handicapped by resource constraints and the whims of hospital laboratories and radiology departments only to perform certain tests under strict conditions.
Again I can’t speak for your particular GP but I promise you the vast majority really, really want to help. They want to make the right diagnosis and they want you to receive the treatment you need, honestly. The way things have changed over the last few decades, with substantially reduced time for appointments and literally having to beg (in fairness equally overstretched) hospital departments to see patients has led to the enormous decrease in job satisfaction amongst primary care staff you hear about in the media. They won’t necessarily tell you this as most try and present a united ‘NHS’ front since they want to inspire confidence in the system when faced with individuals who are in pain, suffering and scared.
Please do keep going to see them but where possible see yourselves as a partnership, trying to solve a wicked problem. They have, thankfully, ruled out immediately life-threatening issues, so awful though you are feeling you have some time to work things through with them.
I don’t want to piss you off but your symptoms do fit a picture of exhaustion, frustration and significant anxiety. There may of course be an underlying deficiency or any of the myriad other suggestions previously posted, but you are clearly (and totally understandably) anxious about what your symptoms mean. With that in mind you really don’t have anything to lose by trying to address this whilst simultaneously continuing to rule out other possibilities.
I have been crippled by anxiety. It took a long time for me to accept this and I had difficult relationships with multiple GPs before I did. When I finally met a GP I clicked with, who pretty much said the same as I’ve tried to write above, I agreed to try CBT. Despite being pretty sceptical I found over time that many of the symptoms started to be less intrusive. With that I felt a lot more engaged and ultimately decided that perhaps the GP was right. That was several decades ago and I’m so grateful I found someone who made me want to trust them. It literally was life-changing.
Good luck, I sincerely hope you get the care you need and perhaps meet a GP you can build a mutually trusting relationship with.