Implantation bleeding...could i be pregnant?

okay try and stay with me cuz its gonna be hard to explain but i rlly need someone to help me out. if your pregnant and ur late on ur period then u start could it be implantation bleeding? like does implantation bleeding happen when ur late cuz im on birth control and my periods are nevvvver late, they always start when i start on a monday of the 4th week. and did not until wednesday. and its rly rly brown i never rly had a very heavy period so its the same amount as always. but nvr brown.