Hello,
At 18 years, possibility of colon cancer is very less. Your difficulty in defecation can be due to constipation. You should make a regular habit of the following – diet rich in fibre- fruits and vegetables, avoid fast food. Drink plenty of water always. Regular exercise will help improve bowel motility.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Now I took a poop it was yellow and a mushy kinda poop...and one of it has a Dark Brown color on only a little part of it...I dont know whats really goin on please help