Spotting 4 days after having sex

Zimme

Hey.  I think I need some help.  I started spotting this afternoon and cramping up.  Also, slightly nauseated after eating something and tired.  Yesterday, it felt really irritated down there and there's a burning sensation when I pee. 

During sex 4 days ago, there was a pinching sensation as if I wasn't wet enough.

What should I do? What is it?