I appreciate how awful you must feel but self diagnosis can sometimes lead you up the wrong tree - and it might not be lupus at all. Save your energy, try not to jump to conclusions ... yet!
I have CD and quite a few AI conditions and what they all have in common is that they share many symptoms and require expert diagnosis - and by this I don't necessarily mean a GP.
But what GPs can do though is to run a lot of tests. You don't say which have been done - firstly I'd contact the surgery and ask them to let you know which tests have been done ... and the results.
Then I'd keep going back to the GP. Take a list of all the symptoms and be very clear about how you feel. you might be able to get an 'on-the-day' appointment with the GP of your choice. In my experience (with quite a few AI problems) it's better to have consistency of care - with a GP you like! - rather than random appointments with a succession of locums. Hair falling out in clumps strikes me as urgent enough for an fast appointment.
In the meantime, and I know this is easy to say, try not to worry. No point in wasting energy thinking you have lupus when in fact it might be something completely different - believe me, I've been there!
Main thing is to persist at the GPs until you're sorted. It might be worth contacting the alopecia soc too to get some support, as whatever the cause hair loss affects many people.
Wishing you all the very best.