Take Action (Plan B) Pill

So, my periods are pretty short, start on Wednesday and end on Sunday, usually. This time it ended on Saturday, and my SO and I had sex a few times during the week I was on the placebo pills. I woke up on Sunday and thought it was weird that my prescription hadn't been refilled so I called and they said I was out of refills and needed approval from my doctor. SO and I freaked out a little bit and went and got a plan b pill called Take Action. Today I experienced unusual spotting and cramps. Could that be caused by the pill or something else? Either way I'm taking a pregnancy test in 3 weeks...