spotting.

Destiny
So my obgyn gave me a sample pack to last me a month before I go for my Pap smear
(My prescription ran out the month before my appointment.)
It's a different brand than what I was on, but I was told I'd be fine. 
Now it's a week before my period is supposed to start and I'm spotting very lightly. 
Obviously there's a chance of me being pregnant, but isn't there a chance it's from me changing pills also? 
I plan on taking a test tomorrow. 
Ps. I do feel a bit of cramping