Your cycles have run 32 to 42 days, so reaching day 36 isn't unusual for you. This alone doesn't mean something's wrong. You also had intercourse around your likely fertile window in late September, so pregnancy is one possibility worth checking too.
Next Steps
Take a home urine
pregnancy test now. It should pick up a pregnancy from this timing. If it's negative, repeat it in 3 to 4 days, since a very early pregnancy can still test negative. If your period still hasn't come by day 45, please see a gynaecologist for a pelvic ultrasound and hormone check.
Health Tips
See a doctor sooner if you get pelvic pain, spotting, or bleeding that's heavier than usual.