This bleeding what you are experiencing is a withdrawal bleed and not an abortion. Pregnancy is not possible as implanon had prevented any ovulation during this cycle for you and in absence of ovulation, in spite of unprotected intercourse fertilization is not possible.
The symptoms you are experiencing are likely due to premenstrual syndrome and they shall subside after the menses stop.
This bleeding in form of withdrawal is usually heavy after removal of implant and you are likely to pass clots as well. If the bleeding is too heavy then you may visit your physician for prescription of antifibrinolytics which can help reduce the amount of blood loss or help stop the bleeding early.
I hope i have answered your query in detail,
Wishing you good health,
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.