I am a science fan/sceptic generally and unfortunately chronically ill. I was saddened to see someone on my rare autoimmune disorder FB group start to spend money on functional medicine which directly contradicted the advice of highly specialised NHS consultants. A quick Google of the term "functional medicine" shows lots of evidence that this is a branch of snake oil sales practiced by ducks. If you want to spend a lot of money on someone telling you what to eat you have the freedom to do what you like. But I personally would not fight the expensive well researched medicine the NHS is providing me with some pre-scientific magical thinking. I hope you find good treatment and comfort.

Sadly there s no scientific basis for " functional medicine "
If it worked the nhs would be doing it

@red1003
Firstly, every sympathy! Chronic illness is rubbish and finding out that you aren't able like you used to be is very disheartening.
In my FB group we look to resources that make us strong self-advocates.
When you see the Drs (GP & specialist):
Take body maps that show where your pain and issues are. Have a really good think about all your past history you can remember: weird injuries? constant viral infections? constant fatigue - how it affects your day to day (hours sleeping/needing more naps than your DC),
weeks of pain diaries scaled 1-10 (eg with my anti inflammatory, full on codeine & DMARD I operate at a steady 6/10 flaring to 14/10! It's what I have to work with 🤷) .
Show that you follow a healthy balanced diet, that you adjust your exercise and do you need physio?
Chronic auto immune & painful illness comes with co-morbidities, often MH ones.
Question your Rx, we build up a collection and GP needs to be reminded if you're worried about contra-indications.
With thyroid know that the range they test is quite wide (11-26). When I first was treated for hypo they said you're 12 so you're fine - well how did they know I wasn't over 20 before?
Your are entitled to referrals, second opinions but you have to fight for them and, exhausting as it is you have to keep on top of it. With all this evidence you might try to get a double GP appointment. And they need to be persuaded why being like this is not acceptable because you don't have the support to put up with it. For the appt get the DC out of your hair so you can pay attention and make them take you seriously (you deserve to be).
If you need to: try to get PIP so that you can use this non-means tested benefit to take up the slack with cleaning etc so you can enjoy your kids more.
Quackery preys on our need to have a positive outlook and find hope... Put that energy into researching evidence based medicine. And do look for support groups for your condition in person and online. There might be a charity for your illness doing medical research - they are the experts you need to follow. Good luck.