Following delivery, some women may experience MILD vaginal bleeding up to 4 weeks which is quite normal. But, if you are on exclusive breast feeding, then generally you do not get your period.
Here, you need to undergo pelvic ultrasound
scan to rule out retained bits or other pelvic pathology. After that, you need to consult with gynecologist for next line management. You may require D & C.
Maintain genital hygiene properly. Good luck.