I expected my period to be here on the 8th of this month.. it is now the 17th and I haven't gotten it yet.. my nipples are tender.and I took a pregnancy test around the 11th and it said negative.. could I still be pregnant?

First and foremost, if you are having sex, there is always a risk of pregnancy.

There are other reasons for a late period besides pregnancy, such as stress and diet. But yes, just because an HPT said negative does not mean you are in the clear. HPT's can be wrong.

The best way to find out is to go to your doctor and have him give you a test. A blood test is the most accurate way to tell, because in early pregnancy some women don't have enough HCG (pregnancy hormone) in their body to pick up on a urine test :)

I agree with star; there is definitely a possibility here. Ask you doctor to preform a quantitative blood pregnancy test.