Hi, I am 18 and concerned I may be pregnant. My last normal menstrual cycle was on the 4th of September. On the 15th of September, my partner and I had unprotected sex, and stopped before well before ejaculation occurred. Around the 24th I experienced reddish brown spotting for five days. Then, on the 4th of October, I experienced a very light period for about a week. For a few days now, I have been experiencing slight breast tenderness and increased hunger. But today, the 18th of October, I experienced ovulation type discharge. Should I be highly concerned of pregnancy? Or could I have had an abnormal menstrual cycle last month and am now experiencing ovulation? Any help would be greatly appreciated.

Any online prediction is merely a guess. I guess that you are not pregnant.
You will find that your periods can often be irregular over the next 35 years or so.