Hi Proud M. B,
I'm a registered nurse and women's health nurse practitioner student, and although certainly not an expert in this matter I can offer what I know is clinically sound advice.
First, this kind of bleeding is not terribly uncommon. Especially if you have been exclusively breastfeeding it is very normal to have irregular bleeding as your body re-regulates. If you have not breastfed your baby, to begin to get near a cause or diagnosis, you'll need to have a pelvic exam, labs (TSH, prolactin), and a give the provider a thorough history. He/she may want to simply have you watch your cycles for a few months and report back, or possibly begin oral contraceptives in an effort to regulate the bleeding. As I mentioned, if you have been breastfeeding this is normal and may be no cause for concern. Either way, a trusted healthcare provider should be consulted, as you know.
I hope this helps.