Help! Does this sound like implantation?

Okay so this past Saturday (July 9th) I noticed light pink/brown spotting when I wiped. It wasn't enough to even get on my underwear, and only lasted maybe an hour. I assumed it was my period about to start but it never came, so I thought maybe it was implantation bleeding. I have also had some mild cramping. I took a test yesterday and it was negative. My last period was may 29th through June 3rd. I should also mention that I have always had very irregular periods due to my pcos but I am on metformin and that has seemed to help regulate my periods somewhat, as I've had them monthly since around march. So I'm not sure if I maybe tested too early or I'm just really not pregnant. It's just strange because I have never had spotting like that before. Has anyone else experienced this, & what was the outcome? Thank you so much in advance!