Bern having light menstruation for 2 months now. iwhat could be the cause?

Many causes...: There are many causes of prolonged light bleeding. For example, during the 10 years prior to menopause, its not uncommon to have months where you don't ovulate. After several anovulatory months, its possible to have prolonged bleeding. There are many other possibilities. If you want to know for sure, see an Ob/Gyn. Best wishes!