Last October/November I started with a set of symptoms that made me think I had a bug - nausea, diarrhoea, stomach cramps, light headedness and generally feeling unwell - which lasted about 24-36 hours. A few months later I had it again and realised it was at exactly the same time of the month, around ovulation. This time I went to a doctor who said it was ovulation pain 
. It then started happening every month at the mid-cycle point (including one occasion when I had actual vomiting) and once happened the day my period started, so I went back to the GP who referred me to a gynae.
Between the referral and the gynae appointment I had two months symptom-free, which was great for me but Sod's law for the appointment! The gynae took a history and thought it sounded more like a gastro-intestinal condition than a gynae one but did blood tests for hormones and Coeliac disease, an endometrial biopsy and I had an ultrasound scan. When I went back for the results a month later everything was normal, so as I hadn't had the symptoms for a few months I was discharged.
However I'm having the symptoms again. I had them two weeks ago (around the day my period started) and I'm having them today (mid cycle). I have no idea what is wrong with me but something is and was wondering if anyone else had experienced anything similar and if so, what was diagnosed if anything?
If it helps I'm 41 and have regular but heavy periods.