Confused about my pregnancy

Hello, so I’m a bit confused and was wondering if anyone had any advice. I already have 2 children but I’ve just found out I’m pregnant with baby number 3.

My last period was August 19th, I took a pregnancy test on September 10th (I know, too early) which was negative of course. I came on my “period” so I thought, a week before I was due. It was a bit lighter than usual, it was more pink/light red and brown and lasted around 4 days.

I decided to take a pregnancy test yesterday as I still had some symptoms, really sore boobs, extremely tired and emotional. The pregnancy test came up positive straight away and I couldn’t believe it so I took another one today which says pregnant.

Do you think this was implantation bleeding rather than a period? Or could I have had a chemical? I’m not bleeding, still experiencing symptoms. Is this normal? I never had bleeding with my first two pregnancies.