Plan B blues

Hi everyone! I'm 21 years old and my boyfriend and I decided to be dare devils and "leave it in" this time. I did however buy a plan B pill and take it 3 hours after intercourse, should I be worried about pregnancy? Just keep an eye out? As of right now I am slightly getting cramps, not sure if this is a side effect. Just would love some feed back! Thank you ladies! ❤️