Pain in uterus! Help!

Ok. So Yesterday I was having sex and my cervix started hurting. I told my SO to stop and change positions to see if that would help. It didn't so I stand up to see if that helps. That made the pain move up into my uterus. Not just any kind of pain. I was literally in tears! The worst pain I have ever felt in my life! It lasted for about 30 continuous minutes then the severe pain went away and I was left with this dull ache. When I stand from a sitting position it feels like an enormous amount of pressure. And today I started spotting 15 days before AF. Any ideas?