My period started on nov 16 and ends on nov 22, I had sex on nov 24. On dec 3, I spotted with smelly brown discharge. Whats going on? Am I preg?

Unlikely. Day 1 of cycle is first day bleeding. Sex on day 8 not likely to catch egg on day 12-14. Preg not likely. Dschg may spotting assoc with ovulation bleeding, and small amount would not run out immed, instead mix with normal discharge and vaginal bacteria broke blood down from red to brown over 3-4 days; if odor from blood persists for 7-10 d, you might have a bacterial vaginosis -doc can fix.