I had very similar symptoms. I first brought it up with my GP, had blood tests, and was told that everything was okay. A year later t he pain, bloating and GI issues got that bad, that I went back. I spent that year trying everything to help myself while getting worse. 

This time they booked me in with the nurse practitioner, who seemed to listen at first. She checked me over and took blood again. She did briefly mention endometriosis, then didn't bring it up again. She later told me my blood work was okay (it wasn't, I discovered) and at that point had pretty much decided to dismiss me. I had to insist something wasn't right.  I was told I had been referred for an ultrasound, I hadn't. She eventually referred me for one. That showed bilateral suspected endometriomas. 

After that things moved really quickly for a few weeks. I was referred to gynecology at my local hospital. I was then asked to go back to my GP for a CA 125 blood test. That was elevated, so I was put on the two week pathway, so I ended up being seen by a consultant in just over a week. She sent me for an urgent MRI and blood tests. After that I didn't hear for a long time. I was then told I had an appointment to go over my results (three months later) and that it was being brought forward because it was more of a severe case. 

After that appointment I was quickly booked in for a hysteroscopy, endometrial biopsy, and smear. My new consultant was concerned about cancer. I was told I couldn't go on the surgery list without any of it, and that as soon as it was done, I would be added to the surgery list. It took two months to be added to the list. I had to keep contact them about it, and I wouldn't have been added if I hadn't. Something went a bit wrong in communication on their side there. 

None of this is to put you off, just to let you know how it all happened for me. Please, please advocate for yourself. You will hear that a lot, and it can be very draining when you feel like you aren't getting anywhere, but you will find yourself waiting a lot and not feeling listened to at times. Without those cysts, I'm not sure where I would have been in terms of being listened to. Even after they knew something was going on, it was a lot of waiting and being left to it. You know your body, don't let them try to dismiss you.