Could I still be pregnant?

Merissa • Married to Caleb. Anniversary 11.2.13.
So, my period was supposed to start Sunday, and it didn't start until yesterday(Tuesday). The bleeding that I have had has been very very light. When I say light, I mean like not enough to fill a light tampon in two days.(I normally have to change my tampon once every hour- hour and a half) And no, that does not mean I haven't change my tampon in two days. Lol
I took a test on Saturday, and it was negative. Could I still be pregnant? Have you ever had this happen?