Hi sorry if this is a long text but I was wondering if it was still possible to have a neuroendocrine tumour with a normal fit bowel screen and normal Calprotectin test?

Ive been having issues for approximately 4 years now with pretty much constant diarrhoea that gets explosive at times. A dull pain in the left side of my abdomen that comes and goes and sometimes spasms if I knock it or move too quickly. 
When these problems started I went to the GP and had a Calprotectin test come back as 127. So the dr referred me for a endoscopy and colonoscopy. Both came back normal so I was diagnosed with IBS.
2 years down the line I started having this terrible facial flushing every time I drank alcohol that covered my face and made my neck go red and blotchy. This usually only last for 30-60 minutes and clears. Even if I keep drinking. I put this down to maybe developing alcohol intolerance so didn't get it investigated. Now 4 years on the redness is appearing on my arms too. It also happens when I'm stressed and the other week it happened when I had a spam fritter for tea!? I get random nausea on and off for no reason. Still have the explosive bowel movements and the dull pain in the left side of my abdomen. 
I returned to my Gp who ordered a FIT bowel screening test which came back normal and then a Calprotectin test which this time came back at 79.
Every time I research my symptoms myself it always seems to say Carcinoid syndrome. But I'm unsure when all tests seem to come back as normal. I feel like I'm just going round and round in circles and it is really getting me down. Can anyone offer some advice? 

Thank you for taking the time to read my message and for any advice given.