Stomach problems. To go for colonoscopy?

Flat stool ( not much) , some time normal , sometime flat (little) , rare constipation & diarrhea , occasionally gas , heavy food causes problem . milk , wheat intolerance , sometime gas causes of pulse . Not blood , no pain , no vomit ... problem persists if I take heavy food in night (mainly) . If I take froot , pure curd , anything pure even wheat then nothing happens. But I afraid to flat stool ( not much thin ) slightly flat. From last 3 months I have observed no pain , no blood , no vomit. Symptoms trigger when I have taken oily or market food. I visited to doctor after compete blood count test , CRP ( reactive protein something ) , and blood in stool .. they have prescribed coloaspa X and probiotics and.... immunobioitics. Nothing happened ...my main concern was about flat stool (why) . Due to this I feeling itching in my anus some time , anal discomfort . Does it is time to go for colonoscopy ? Because doctor one time said for all problem one solution colonoscopy but unfortunat