My last period was on 28.02.14 and I have 6 days delay period. So I am expecting period around April 3rd or 4th But it almost 16 days delayed and still I didn't get period. But yesterday I started what I thought a period but it was only a smear rather than normal. I have nothing now. Just one drop.I didn't have period symptoms either, no abdominal pain or breast sensitivity either.No treatments or medicines taken, no other symptoms.
I have taken pregnancy test, but its negative. And we had unprotected sex and expecting too.. Could you please help us with this matter? Is there any chance of having pregnancy in this case?

There is a good chance of pregnancy. When did you do the test? You should try another on or go to your doctor for one. Use the early morning urine.