I am 42 and experienced the same symptons for a good 6 months. My blood tests were normal and my stool test didnt show anything. I had to push for a FIT test (this tests blood in the stool, stool test doesnt check this), I had occasional red blood on my toilet paper after wiping but this comes from lower down, bleeding higher up doesnt show so obviously. I was in constant discomfort, blaoting, pain, fatigue, sleeping terribly. The 3 months up to New year were particualrly bad, i started self treating my constipation with a lot of cabbage, broccol, brussel sprouts and the like. This was a mistake, athogh it helped with the constipation, it made the cramps and bloating worse. So bad that i could only go outside for 20 min on NYE before having to go home again in massive discomfort and uttterly exhaiusted. I cant say I found the GPs paticualrly helpful or sympathetic in this case. Finally I stumbled on The low FODMAP diest and have been following strictly for 3 weeks (will contonue for another 3). I felt better after just a few days, my verrsion is basically just rice porridge, ginger, carrots, parsnip and kale and lots and lots of herbal tea and propcorn-almost nothing else-  it is not great. after 3 weeks my movements are really pretty normal. It seems I have IBS, not even IBD or bowel cancer (which i thought at first). Cut all (i mean ALL) normal food out and try this. You are doing the right thing by seeing the GP, but if the tests come back normal and your exp is anything like mine, they wont offer much advice beyond this.  Given that the pain and discomfort is clearly real. this didnt really put my mind to rest. a few weeks of Low fodmap diet has helped a lot.