Hello dear
Understand your concern.
Contraceptive is type of long-acting reversible contraception, the most effective form of birth control.
It inhibits the ovulation and implantation.
Common side effects of implanon are below:
Irregular bleeding and spotting
Delayed period,
dysmenorrhoea
weight gain
Ovarian cysts
Acne
So I think it may be side effects of implant.
It is generally due to hormonal imbalance
If not resolved
You can consult the gynecologist for other cuase like
Endometriosis,
Dysfunctional uterine bleeding, fibroid,
cervical dysplasia, cervical poly, ovarian cyst
Do the full hormonal profile like E2, FSH, LH, pogesterone, HCG, Prolactin, Thyroidprofile.
If necessary
endometrial biopsy, follicle study and USG.
Hope this may help you.
Best regards
Dr. Sagar