Hello Good Evening,
You seems not a pregnant, because you had a period after unprotected sex i. e. you are not pregnant because of sex done on 18th November, because you had next period on 3rd December.
Please go through following points:
1. You got a menstrual period after sex, which totally rule out your pregnancy
2. You had 2 days bleeding in menstrual bleeding, which is normal (usually normal range of bleeding 3-5 days but can be 2-7 days).
3. you have delayed period now, means your LMP date is 3rd December and this period should be started around 3rd of January, so you have delay about 7 days, so find the unprotected sex date during this cycle i.e. in December.
So you are not pregnant because of 18th November, since you had a period after your unprotected sex, but can not comment about delayed period now, without knowing your sex history of December.
One more thing you should aware that, weeks of pregnancy always counted from LMP date, not from unprotected sex date.
Dr. Naresh Jain.