So confused!!! Any advice re implantation?

So yesterday I started spotting, right on time for AF. Usually I spot for a few hours then get AF. This morning I woke up, spotted all day (only when I wipe) and still no AF? So I did an opk (last pregnancy I got a positive opk before hpt) and it's close to positive, but not quite.

So confused! Is this AF? And why hasn't it started yet? Surely if I was pregnant it would show up strong by now at 15dpo, even on an opk?

I only have one hpt, do you think it would be worth testing in the morning?

Isnt this way too late for implantation? Surely if it is, it wouldn't be a good sign for a viable pregnancy?

Those who had implantation bleed, was it just old blood or fresh and how much/how long did it last?

Gah!! Just be one or the other!!