Firstly, well done in contacting your Dr to discuss your  symptoms, it's a brave first step.

Full bloods can show a number of things so are a good starting point for their diagnosis route. An ultrasound may have been requested to investigate gallstones which often present themselves as pain under the ribs, I've had these and goodness they are painful. Your Dr may be taking a cautious approach as the hospital is likely to be running a reduced service in some areas. Endoscopic procedures including colonoscopies are classed as higher risk procedures in relation to Covid-19 so may not be their first line of investigation for bowel complaints if alternatives are available. 

I hope that all goes well, there are lots of us here to support you so please don't be afraid.