Not meaning to offer a diagnosis or anything- but it sounds like IBS, irritable bowel. I also would not be certain you are so anaemic because you're bleeding. They don't really seem to think so or you would have gotten an MRI or something. The normal range is 20-a few hundred, not sure of the upper limit. Haemochromatosis- too much iron, is much worse. Below 13 is seen as anaemic. My first symptom of IBS apart from increasing wind was a strong pain in the left abdomen after eating that I couldn't walk straight. Followed quickly be a general abdomen pain, quite severe. Wind, bloating etc. are also very common symptoms. What would be helpful for your GP is if you can describe the pain accurately- waves, constant, does it peak, short and sharp...location- lower left, lower right, centre..etc. and if anything brings it on..ie. eating. The thing is with IBS if that gastroscopies and colonoscopies will show up as normal. They need to rule out stomach ulcer, Coeiliac, crohn's disease and ulcerative colitis first. Biopsies taken will probably have ruled out coeiliac though, as well as ulcer.
Not to say oh it's DEFINITELY IBS but it's an avenue worth exploring. In the meantime I'd recommend Colpermin or peppermint oil tablets/tea. They can help relax the spasming muscles which are causing the pain. (Or probably causing the pain. They would do no harm anyway). Best of luck with getting to the bottom of this.