I am a 24 year old female... I have had a reliably 27-28 day menstrual cycle for years now, with a once or twice exception of 29 days. My last cycle started on August 13. This current period (??) started mid day of cycle day 31, which is very rare for me.
My periods *always* last 5-6 days, and usually start off medium flow for the first day, heavy for the next 3-4 days, and medium-light on the last day until it finally ends..

This current period, aside from being a few days late, started with just spotting watery red and rose colored on the first day.. Not enough to ever make it to a pantyliner, just when I wiped.
The second day was a brighter red.. a bit heavier, but only had one tampon in, and used a pantyliner for the rest of the day, as there was no flow, only stringy slimy blood, some clots, and what seemed to be a lighter colored tissue when I used the restroom.
Today is the third day.. I put one regular tampon in for the morning and when I took it out after lunch, there was a small bit of red and brown blood on it, but not enough to soak through, and made it uncomfortable to take out..
Now when I use the restroom, there is no flow, clots or tissue.. Barely anything -if any- when I wipe.. Have had a pantyliner for 2 hours and no sign of anything.
It is the 3rd day and seems as if it is the very end of my period on the usual 5th or 6th day.

I had unprotected sex about 8 days before my expected period, using the pull out method.
I had slight cramps on the expected period day, along with slight cramps on the day i saw spotting, as well as extreme moodiness and headaches. I do not have any more symptoms of PMS (or pregnancy), not even my usual achy breasts.

Is this something I should be worried about? Is there still a chance of pregnancy even with the "period" and timing of the intercourse?
Would you recommend taking a pregnancy test? Seeing a doctor about my unusual period? Or waiting it out and see if the next one is normal?

Thanks for your help!!