Brown discharge and light bleeding after unprotected sex can potentially be signs of pregnancy, especially if you recently stopped using contraception like the family planning injection. This could be implantation bleeding, which occurs when a fertilized egg attaches to the uterus lining. However, it's important to note that there can be other causes for such symptoms as well, including hormonal changes or irregular periods. The best way to determine if you are pregnant is to take a home pregnancy test or consult with your healthcare provider for further evaluation. They may conduct additional tests or examinations to confirm whether you are pregnant or if there is another underlying cause for your symptoms.