Hello,
Lochia persists for close to 6 weeks after delivery and not beyond that. The bleeding that you are having can be due to side effects of the Implanon. You can discuss it with your gynecologist and get it checged. If the bleeding persists then menorrhagia should be ruled out.
Excessive amount or duration of menstrual flow, at more or less regular intervals is called menorrhagia.Sometimes it is associated with polymenorrhea(Frequent flow, cycles of ≤21 days)Causes of menorrhagia are Hypothyroidism, Endometrial proliferation or hyperplasia like ovarian tumor and polycystic ovarian disease,endometrial polyps and neoplasia,endometriosis,fibroids and uterine sarcomas.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
At first you can bleed for awhile post partum but I would consult your doctor and let them know sometimes the cervix doesnt close the whole way and you keep bleeding!