Is it my period?

Usually the second day into the dupes, I start my “period” but the blood is mostly brown and either chunky or watery. My flow is also very light. I get usual period symptoms but I’m not sure if I am truly just spotting. I am thinking I might be pregnant. I am just starting my period today and I feel nauseous. I am sexually active and the pill is my only form of protection. I take it every day but the timings can be a few hours off. What does it sound like to all of you? How do I know if its my period or implantation bleeding?