Can break through bleeding mean pregnancy? On nexplanon? Or is It a normal side effect?

Nexplanon. Nexplanon can cause irregular bleeding and spotting. This is a normal side effect of this birth control method. If this is a change from your usual pattern consider scheduling a visit for STD testing. If you think you might be pregnant check then check a home pregnancy test. They are cheap, reliable and available at any pharmacy. Bleeding does not indicate pregnancy.