Could Pinkish Brown Discharge Be Implantation Bleeding?

hi, i am 32 yrs old and ttc for almost 2 yrs. i am 10 dpo and supposed to start my montly cycle in 4 days. i have very regular periods all though sometimes i may start a day or two early or a day or two late. this morning when i used the bathroom, when i wiped there was a smudge of pinkish brown. i thought i may be starting my period but nothing else has happened. we have not had sex for two days so i knew it wasn't that. could this be implantion bleeding?