HELP??

I'm getting a little worried. I was on the pill for a month and had my period about a week in while I was on it. Two weeks after that period I stopped taking the pill and I had another period. I am very sexually active but I use a Condom every time. I have logged all my periods, but eve tells me I'm 9 days late. I took a pregnancy test yesterday and it was negative. Could I still possibly be pregnant or is it the birth control?