I have had a 28-35 day cycle since July this year and it is December and I cannot recall being later than 35 days, but then again I've only really been keeping track for less than a year.

I had my period July 4th (35 days) August 8 (28 days) September 5 (30 days) October 5th (33 days) Novembr 7th.

So, my last period was on November 7th. On day 21 of my cycle, November 28, I believe I ovulated because I had spotting that looked like very old blood. The blood was dark brown, almost black and it lasted about two days and I had to wear a pad. There's no way that was my period as it was way earlier than my normal cycle, right?

I have NOT had intercourse ever. The only sexual activity my boyfriend and I have is oral and dry humping but we are very careful. We keep on ALL our clothes when we dry hump, meaning we both have our underwear and our shorts on and he NEVER finishes on top of me, even when he's only humping my butt and not the front. When we do oral, he won't go down on me if I've already went down on him and we've kissed just in case sperm travels through our saliva. He also doesn't let me touch him anywhere near there nor does he touch anything of mine (like my bed) unless he's washed and wiped up (TMI SORRY!).

It is now day 36 and I have not gotten my period, only very almost unnoticeable little streaks of discharge on my underwear and nothing when I wipe. I cannot tell what color the discharge is because my underwear was yellow, therefore I'm not sure if the discharge was a slightly darker yellow or just white.

It's basically impossible that I am pregnant, so why is my period late? I am 18 years old.