I've dealt with it myself and it isn't nice at all especially if it begins to hurt and burn on your tongue or even spread down your oesophagus.
From what I've read and heard Oral thrush can be caused birth control pills. Many other things such as a dry mouth, medical conditions such as diabetes and HIV. There is such a list of things that can cause it. Some say home remedies such a yoghurt and Apple cider vinegar can help treat it. However the best option is to go to your doctor and get tests done just to be sure about your general health. You should be given anti-fungal medicine which should clear it up within a couple of days. Good luck.