Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain constipation
can occur due to a number of causes like sudden change in dietary habits,excess intake of dairy products,excess intake of antacids,eating disorders, lack of dietary fibres,side effects of medication,thyroid disorders, Irritable Bowel Syndrome
As colonoscopy came back to be normal there seems to be nothing serious..
You can also do blood tests to rule out for hormonal conditions and other causes..
As of now you can start taking high fibre diet an along with it take fibre supplements
like Psyllium or Lactulose..
You can continue taking Pegred or Polyethylene Glycol
You can take stool softeners like Docusate..
Take more of green leafy vegetables and fruits..
You can also be advised prescription medicines like Lubiprostone
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.