I had this over 40 years ago so although medical treatment may have changed I'm sure the symptoms are the same.
Around teatime I was seized by a sudden and excruciating pain in the right side of my abdomen. When that subsided I was left with intermittent pain. I had no idea what was going on but I had a warm bath before going to bed and having a very disturbed night. The next morning I went to the GP who suspected appendicitis and sent me home with instructions to go to A&E when it got worse. At the hospital they agreed with the GP's diagnosis but when they operated my abdomen was full of blood from a ruptured ovarian cyst. They removed my appendix and the cyst. I had no idea I had a cyst but the pain was acute and recovery was rather slow and uncomfortable. Thank heavens for my Mum who came to look after everyone, including a newborn. I wish you well Sparklefizz