Please understand that one symptom alone cannot.be considered as cancer.You have mentioned pencil like stools and there was associated constipation with associated mild bleeding.There might be several reason for the above issues.You haven't mentioned anything about recent change in diet or whether you are drinking adequate water or whether you are having sedentary lifestyle.All these factors can cause constipation also and it can be relieved by correcting these factors.
Next Steps
Since I donot know your proper history and I donot want to neglect the issues mentioned by you,I suggest you to consult a Gastroenterologist nearby.If something noteable is there..he might suggest you a colonoscopy ( note: if the doctor feel it's important for you to undergo that) Colonoscopy is not only to see whether you have cancer but can diagnose a lot of conditions .So don't preoccupy your mind with thoughts of cancer