Worsening upper GI symptoms - worried

Hi all new here. I've had GERD/reflux for many years, had a Gastroscopy in 2006, diagnosed with gastritis, then in 2011 a further scope showed stomach erosions. In 2016 I had a gastroscopy (mild inflammation in oesophagus) and colonoscopy, where I had colon polyps removed (benign). Since then, my reflux has been chronic and persistent. I have spoken with my GP on many occasions over the past 5 years and have just been prescribed different PPIs, none of which seem to be very effective. H Pylori tests always negative. I don't smoke, hardly drink alcohol, avoid spicy foods/most of the trigger foods. 

Over the past 2 - 3 years, I have been experiencing left sided abdominal pain (intermittent), with left sided reflux symptoms, regurgitation of foods, burning sensation, bloating, feeling of heaviness in left abdomen and left side of esophagus, tiredness. No abnormalities in blood tests apart from ESR our of range (but not extremely high). The past few months, all my symptoms have worsened as has the fatigue/weakness. I have gone off/can't stomach certain foods which I previously liked (chicken, vegetables), meaning I'm eating more 'junk'/high sugar foods, as I feel I can tolerate these. I did 2 FIT tests, which came back positive, so GP has referred me for a colonoscopy and gastroscopy under the 2ww, which I'm due to have on 2nd September.

I know only a medical professional can diagnose me, but I can't help worrying about the possibility of cancer, especially as symptoms have been chronic over many years and have recently worsened, plus with the fatigue and positive FIT tests. It's on my mind all the time. Also frustrated that GPs haven't been listening to me over the years re PPIs not helping my condition. Not sure what I want from this, but just felt the need to vent.