Hello. My Concern Is About My Period. The First Day

Hello. My concern is about my period. The first day of my last period, was the 22nd of July. I'm a few days late on when its due. And last nigh, I had a little bit of bleeding. It stopped until 7 pm the next day. Its light pink and very very light. My normal periods have last 6 days and have always been heavy. But, I have had sex 4 times this week. Could I be having an irregular period or the implantation bleeding?