Ive Had Implanon For 4 In Half Years Never Had

Ive had implanon for 4 in half years never had a period while on it. After the 4th year wicth was may 15th. i had a light bleeding. Didnt have another for 3 months had one on july 14th an bf an i had unprotected sex an he did it in me alot that month. Didnt have any periods. Had a hour light bleeding on sept 26. Could i be pregnant? Is the device wearing off?