Welcome to Healthcaremagic.
From your Query i understood that you are confused about whether you are conceived or not.
Most probably it could not be a symptom of pregnancy
usually occurs after 6 or 7 th day of fertilization of ovum.
Your ovulation date was around 21st december.
If that egg got fertilized, then implantation must be either on 28th or 29th december.
But you are experiencing symptoms for 2 days.
So it vomiting may be due to food poisoning
After implantation only, the hormone level changes in blood. Just fertilisation, cannot cause change in blood hormone levels,
Hope this helps.