Hi there ,
I have understood your concern. I will suggest you the best possible treatment option.
First of all do not panic.
Implants like Nexplanon ,if fitted in first 5 days of the menstrual cycle,it starts working within first 7 days. In a woman with regular cycles it is anyway safe period till day 10 of the cycle.So you can have unprotected sex in this condition.
If fitted later . you need to use barrier method like condom for at least next 15 days.
I will suggest you to use
i pill or
Plan B within 72 hours of unprotected sex activity.
If this time periods is lapsed by now, you can wait for your expected date of cycle or till 15 days after your sex activity , and get urine
pregnancy test or blood
beta HCG test done to rule out pregnancy.
As with Nexplanon , you may or may not get your nest cycle in a regular manner; just do not wait to get your next menses .
i hope this answer helps you.
Thanks.
Dr. Purushottam Neurgaonkar.