As for a possible thyroid problem - I had a medical check-up earlier this year and I appeared to have low blood pressure, but when I returned for a follow-up appointment my blood pressure reading was normal, so that was that. I did get referred to mental health services for showing symptoms of anxiety, but so far all I've had from them is a prescription for anti-depressants and two brief sessions with a shrink. The second session was back in June, after which the analyst was moved to another role, and I've had to wait until now to be given another appointment (for next week).
To eliminate hypothyroidism you have to have a blood test. Unless your GP is a bright spark he may not know much about it. Even the lipid consultant I saw at St Thomas Hospital missed it, he tried to treat a symptom (high cholesterol) not the cause.
At the moment it's been hard enough getting the doctor to call me back (or at least when I'm available to take the call), let alone make an appointment.