Being 'sick' is no valid symptom. Are your breasts sore? Is your belly hard? Is your belly growing/bigger than normal? Do you have weird cravings? That's four months between September '12 and January '13. Best answer is to go buy a pregnancy test.
If he ejaculated in you, there is a good chance of pregnancy if it happened in a fertile time. However you don't give much in the way of clear detail.
- What was the first day of your period? 5th Dec?
- What is your cycle length? 28 days? Is it regular?
- When did you have sex? 9th Dec?
- When was your Jan period due? 2nd Jan?
- Have you had any sexual activity since? If so what, and on which days?
If the assumed dates are correct, then if you ovulated 5 days earlier than would have been expected, then it could have happened in a fertile time. If you had other sexual activity, sperm might have been transferred (maybe manualy) to your vagina. Then again, you may have just missed a period.