should i take plan b?

So I've been on the pill for about 2 months now and yesterday was the first time I let my boyfriend cum in me. I had stomach pain that day and diarrhea and I read that if you have diarrhea or vomiting it may make the pill less effective. Also tonight i woke up at 1 am sweating nauseous and w diarrhea as well. Ik it's way too early for pregnancy symptoms so i think i have the stomach flu. Should i take plan b to be extra safe??