Extreme pelvic pain? Help!!!

I've been ttc for a while. Friday I was out shopping when I checked out and walked to my car I was hit with a sudden pelvic pain that was so painful I couldn't drive or sit down. When I got home I thought it was gas so I went to the bathroom and couldn't even push without the pain there. So I waited and after an hour it went away. I didn't feel any pain the rest of The night. So Saturday I decided to have sex thinking nothing was wrong. And bam instant pain while having sex and even more so after. So I got so scared I went to the drs. All tests and exams came back negative. Nothing was wrong. What the hell!!! No bleeding no spotting nothing. No one gave me answers. I just went to my ob today and I go for a ultrasound Thursday she thinks it's a cyst. Anyone have this problem or pain? I was hoping to be pregnant but now I'm scared to death about this.