Is this spotting for pregnancy?!?!


Last week I had unprotected sex on Monday and Tuesday. He pulled out way before on Monday but on Tuesday we thought we might have cum inside me a little before he pulled out. On Wednesday, I went and bought plan B (brand: take action) and took it right away. I am on birth control but i had just started a new cycle on monday so it worried me. We did continue having sex once on thursday but he pulled out way before again. last night, (tuesday of next week) i went to the bathroom and saw that when i wiped, there was a light shade of blood. I haven't had any cramps. Is this a sign a pregnancy? Or a side effect of taking plan B? I am so nervous and i'm trying not to stress out because stress can delay my period further on so I'm really looking for an answer here.