Hello, Thanks for writing to us. Irregular spotting or abnormal bleeding is quite common side effect of birth control Implant like Nexplanon for first time user. It will overcome with the time period. However, we need to rule out or clear doubt about early implantation bleeding (very low chance) by undergoing home pregnancy test. Other reasons are old blood, endometrial tissue, hormonal imbalance, stress/ depression, irregular diet habit, vaginal/ pelvic infection etc. Please, consult with gynecologist for complete health check up with relevant investigation. Take proper medication accordingly. Maintain genital hygiene. Avoid mental stress. Good luck.