When dealing with hair loss
or thinning, it is first important to determine whether there is an inflammatory or infections or other condition in the scalp that could be leading to the hair loss or not. Given your symptoms of itching scalp, I think this is particularly important. Conditions that could be associated with hair loss include seborrheic dermatitis of the scalp or a fungal infection of the scalp, among others. I recommend going to see your primary care doctor
or your dermatologist
to rule out these conditions.
Assuming these conditions are ruled out, then the approach to hair loss includes ruling out other medical conditions which can cause it, principally problems with the thyroid gland and iron deficiency, both of which can be ruled out with simple blood tests. If these conditions are ruled out, then the most likely cause of your hair loss is something called telogen effluvium. This is a condition in which hair loss occurs because of some stress to the system. This is usually a new medication or an illness, but in your case it could also be simply the stress of changing to a night job.
Talk to your doctor in order to get a diagnosis and determine if treatment is needed.