In my experience, you would NOT be experiencing pregnancy symptoms only 4 days after the event.....it sounds like you have a virus, or maybe are sick from worry??

Believe me, I've made myself crazy wondering about getting pregnant in really unlikely circumstances (like...if we have sex, and the condom DOESN'T break, what are my chances of getting pregnant?!) Every time, it was a LOT of time spent worrying and freaking out, followed my....my period!

I hope you start soon so you'll feel better.