Possible Pregnancy with Implant?
If your girlfriend had the implant inserted 4 months ago, then she definitely should have been protected from unwanted pregnancies for over 3 months. According to Planned Parenthood:
The implant is one of the best birth control methods out there — it's more than 99% effective. That means fewer than 1 out of 100 women who use Nexplanon will get pregnant each year. It doesn't get much better than that.
If you get Nexplanon during the first 5 days of your period, you're protected from pregnancy right away.
If you get the implant at any other time in your cycle, use some other form of birth control (like condoms) during the first week. After that first week, the implant starts working and you're protected from pregnancy for up to 4 years. That's why it's called get-it-and-forget-it birth control.
If you are still having concerns or just want peace of mind about this, the best thing to do would be to take a home pregnancy test, or have your girlfriend meet with her primary care physician, gynecologist or adolescent medicine specialist to give her a pregnancy test. If you are worried about an incident that happened between the two of you one month ago, you would be able to do a pregnancy test any time.
If you don't have a doctor and live in northern New Jersey, you can call the Adolescent/Young Adult Center for Health at 973-971-5199 for an appointment with an adolescent medicine specialist or contact your local teen health center or Planned Parenthood. A Planned Parenthood health center is a good option if you have concerns about cost or confidentiality issues. You can also contact your insurance company for a list of in-network providers.
FX also suggests that you and your girlfriend check out the links in our Resource of the Month: Planned Parenthood Resources on Safer Sex so that you can learn about sexual readiness, how pregnancy happens, pregnancy tests, emergency contraception, birth control, STDs and more. The more educated you are about these topics, the more likely you will make healthy decisions for yourself when it comes to your sexual health.