Whenever a hair loss problem develops, the first thing to do is to go and see your GP. They will help you get to the root cause of your hair loss and only then will you be able to treat the condition correctly.
As part of the process, you are likely to have to see an NHS dermatologist. While dermatologists are commonly thought of as dealing with the skin, they also deal with hair, as hair follicles reside in the skin. However, there may well be a wait to see an NHS dermatologist. If you cannot wait, you do have another option. You can an appointment with a trichologist privately.
Trichologists deal with the hair and scalp and a typical consultation is an hour long. As with any medical position, there are qualifications for trichologists, so make sure you are being seen by a professional.
During you hour-long session, the trichologist attempt to diagnose your problem and should be able to recommend a subsequent course of treatment. If your condition is likely to result in substantial loss of hair, there are various hair replacement options that you can take a look at to help you manage the problem.