I had period on 1st Feb, and had unprotected sex on 9th Feb. I have been feeling abdominal pain for 14th and 15th and had spotting of nearly brown colour on 14th. Can I be pregnant? If yes, When Can I take pregnancy test?

Anytime you have sex pregnancy is a risk. You'll want to wait until after your expected period and test with first morning urine. If you get your period, but it is spotty, light, short, or otherwise unusual, you may want to test anyway. If you are not trying to conceive, this would be a GREAT time to look into some birth control if you are not pregnant, and if you are trying to conceive then I hope you get the result that you are looking for.

Of course you could be pregnant after 6 days of sex, but you have to wait until you miss a period to find out.

"6 days of sex"? Where were you when I was 20? LOL Or did you mean 6 days after sex?