can implantation bleeding last 4-5 days?

[rebeccalouise]

I started spotting like pink/brown on Saturday, it's only been when I've wiped, nothing in my pants. Yesterday, it turned to red and I had a small spot on my knickers. Today, it's completely stopped! I'm due on Friday. However, I have PCOS so I'm normally on heavily every two weeks! This month, I've had nothing but this spotting and I'm certain I ovulated on the 19th. I did a test on Sunday, 9dpo - it was negative. But, that was before this red spot yesterday. I don't have any pregnancy symptoms, but not bleeding for this long is so unlike me. I want to get my hopes up, but I'm trying so hard not to, as I usually end up devastated every month.

So, my question is, could this be implantation bleeding, or has it gone on for too long? When should I test? Thanks.