I've been on bc for 4 months. I missed a pill 3rd month by six hours on the 2nd week and had intercourse the same day, got period, 4th month spot?

Periods. Unfortunately, any time you miss a pill, even by just a short time, there is a small chance of pregnancy. Therefore, you should see your Family Doctor or Gynecologist to have a blood pregnancy test. If that is negative, then things should normalize over time.