I know it's incredibly hard but try not to worry. I experienced similar last year. After three consecutive months of intense period pain, disabling fatigue the week before and week of period, heavy bleeding, bloating (I'm frequently bloated as have IBS so wasn't a new symptom for me), etc I went to the doctors.
Was given an appointment with the nurse practitioner which I think helped as I am sure one of the aged male partner GP's would have fobbed me off as you have been.
She prescribed a form of anti- inflammatory for the pain and referred me for an ultrasound due to my age (I'm 43).
Results showed that I had a large complex ovarian cyst and would be sent an appointment for a follow up scan in 3 months time (it ended up being almost 6).
That's all I was told, that these things are fairly common and resolve themselves so it's best to use the "wait and see" approach. The GP giving my results did add that should I experience a sudden excruciating pain then to go ti A&E as it may have ruptured.
Of course turned to Google and all I could find was women commenting about these types of cysts on cancer forums. My grandma had ovarian cancer so I worked myself up quite badly at times but I had had blood tests done at the same time which were all fine so I just told myself not to worry due to that fact.
I now know that ovarian cysts, even large and complex ones, very, very rarely indicate cancer or anything menacing.
The pain & bloating continued, especially on my period. I could feel the cyst through my abdomen it was that big (7cm) compared to a teeny 2-3cm ovary, but I think it did start to ease a bit month but month.
When I finally got the follow up scan I was told then and there by the sonography what she could see. There was no sign of any cyst, it had completely resolved itself.
She commented that there were a few fibroids but that all was normal.
Her comments were followed up by a letter from the GP saying the cyst had resolved itself and therefore I was discharged. No mention of the fibroids and I'm yet to follow up on that.
So please try not to worry. Is the MRI being done privately too? Was this recommended by the hospital? Did they say why? Have you had any blood tests done?
I still have more painful & heavier periods than I used to, which has been a constant since January last year, so do need to push for further investigations I suppose, but believe I may be peri-menopausal where I've read our monthly's do get heavier and more painful - oh joy!
I hope some of my experience helps 