So firstly I am sorry that you are experiencing this. I would however suggest you do not need to see an Endocrinologist at this point, unless you want to go privately. However you will need a number of specialties if so, but your GP could help with all of these.
Your symptoms firstly require an ultrasound regarding your bleeding. Following on from this managing your periods with a combined contraceptive would help with this as well as PMS and subsequently your mood if so. If this does not help, then your mood should be addressed with anti-depressants if you are getting suicidal thoughts.
Your blood tests in August were normal including your thyroid test, however you have repeated only some of these in September which now shows that your TSH has risen. Therefore repeating this in another 4-6 weeks to see if you are developing Hypothyroidism. This would explain the mood and weight loss as well.
Unfortunately a sweet tooth is a but of a achilles heal, however unless you can overcome this, and there is no other cause to treat, losing weight will indeed be near impossible. However if you feel better with your mental health, you should find it easier to manage. You should also not consider it a diet, but a lifestyle change. If you curb your sugary food only to lose weight, it will come back if you return back to the same diet unfortunately.
I would ask your doctor to arrange a ultrasound pelvis scan, and repeat your thyroid function and see what it shows.