Plan B causing horrible cramps

Okay ladies I need to know if this is normal or if I should actually be concerned. I took the plan b pill on Thursday and today is Sunday. I'm cramping so bad it's making me nauseas. it's like hard cramps that Almost make me feel like I need to poop. 
I also noticed my skin cleared up, I have acne and my face is spotless. I guess that's a good thing but these cramps are murdering me. Like I've been in a hot bath for 45 minutes because it's the only thing that's soothing it. I am not bleeding at all. 
Added: I did read the side effects online. I know that cramping itself is normal. But I don't think my cramping is normal.  since I posted this the cramping has gotten worse and I'm literally shaking from the pain.