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Implantation generally occurs about 7 days after ovulation, so if you had implantation bleeding, it would have occurred about 10 days ago. Bleeding can stay in the vagina for a day or two, but not much more than that.
Since your period is late and your pregnancy test is negative, it looks like you didn't ovulate this month. Most women will occasionally not ovulate, often due to stress. When ovulation doesn't occur, it generally causes a missed period plus other symptoms such as tender breasts, fatigue, and emotional changes.
Usually things will get back to normal with time. If you have had much stress, I would work on that (exercise, good nutrition, sufficient sleep, etc).
How do you know that you ovulated?
It is possible that you had egg white mucus but did not ovulate.
If you had ovulated, then your period should have started by 14 days later, or you would be pregnant.
Implantation usually occurs 6-8 days after ovulation, but perhaps can be as much as 12 days after. So I guess there is a slight chance that you got pregnant, implanted late, and haven't had a positive pregnancy test yet. My bet is that you didn't ovulate.
In any case, with regular ovulation and tracking like you do, there must be some other problem, since it took you 18 months to get pregnant. I hope you've seen your doctor about it.
There are many aspects to PCOS, but the basic problem is not ovulating much. Having very regular periods makes the diagnosis suspect.
It is possible to have regular periods and not be ovulating, but it would be unusual.
The way to be sure if you're ovulating would be to do a blood progesterone test 1 week before the next period. It's also possible to track ovulation with ultrasounds, but that requires doing an ultrasound both before and after ovulation.