Dear Piffle,
This may be completely wrong, but worth a shot!
2 months after my dd was born, I developed a very severe pain in the left hand side of my groin, exactly in the place where I have previously felt ovulation pain. I started throwing up and shaking and eventually went to A&E and was admitted for 4 days. They decided I probably had kidney stones and one was moving. However, nothing turned up on any scans etc. 2 months later the same thing happened again and this time they checked me out for a pelvic infection and gave me IV antibiotics. Again I was admitted and stayed in for 4 days. When the swab results came back, there was no sign of infection at all.
Now, I'm waiting for an appointment for a colonoscopy as they want to investigate my bowel. I now have this pain in a milder form quite regularly, with occasional flare ups which are much more painful. The Drs now think I may have diverticular disease, or possibly Irritable Bowel Syndrome.
Have a look at this
and this
I was told that it is sometimes quite difficult to diagnose abdominal pains in women because the gynae bits and bowel bits are very close together so the pain when you describe it could be in either.
I was SURE the pain was from my ovary, but when I was scanned, everything looked fine.
As I say, this may be completely wrong for you, as diverticular disease is more common on the left side, but it might be worth a look! Let me know how you get on.