Hi thanks for your question.
The symptoms you have described are all of Diabetes mellitus
that is increased in blood sugar level. You are having classical symptoms of dabetes.No1. Polyphagia that is increased hunger. No 2.polydipsia that is increased thirst and No 3. Polyuria that is increased urination. Other symptoms like dry lips, calf muscle cramps
are due to dehydration
as consequence of increased urination. Thrush is fungal infection
more common diabetes due to increased blood glucose level. Change in colour and splitting of nail is also part of fungal infection more common in diabetics as explained. Back pain,tiredness is due to weight loss
which occurs in diabetes as consequence of more protein break down. First thing you do is go and get your fasting blood sugar and urine examination done. Consult a physician who may examine you, may advice you more investigation and put you on treatment.
Hope this answers your question.