Missed period..could i be pregnant? please answer?

I've Been on yasmin for 6 months i missed a couple of pills in last months pack it was about 3 pills in a row in the first week then 2 in a row in the second week. ....my period is now a week late. and i did have some very light spotting about 2 weeks before my expected period was suppose to come down, i took a test last week and it was negative( 5 days before my expected period).... my period is now a week late...could i be preg? could it be too early to take another test? i have been experiencing nausea especially at night.