Does nexplanon birthcontrol start to loose effectiveness before its expiration date? on my last year and worried about pregnancy

Some basics: This form of BC has been approved by the FDA to be listed as effective for AT LEAST 3 Years from data submitted during the approval process (that takes years). There are some medications that can interfere with its effectiveness, but it should be considered safe & effective for that duration. If you are really concerned discuss this with your doc and or use a backup BC.