You should see your primary care doctor
for further evaluation of your rash. Based on your description, the rash may be a type of "contact dermatitis" caused by contact with some form of irritant to the skin, such as the collars of your shirts or a necklace. Another possibility, as you mentioned, is a fungal infection. Superficial fungal infections of the skin often take the form of a ring (hence the name ringworm) and are often red, scaly, flaking and itchy.
Since it isn't clear which of these processes is affecting you (or if you are experiencing a rash from a different cause altogether), it would be advisable to see your doctor. Applying over-the-counter corticosteroid creams to a fungal infection may actual make the infection worse or alter its appearance, making it difficult to make an accurate diagnosis at a later time. Your doctor can either make the diagnosis based on exam or may choose to look at cells from the rash under the microscope, which can often identify fungal organisms. In the case that a fungal infection is diagnosed, treatment with topical antifungal medication should resolve the problem. Oral medications can be given in the event that topical therapy fails.