Prolonged bowel and prostate issue

[slippingintothedark]

I am a 23 year old smoking, male with no family history of prostate or colorectal issues. My mom has back and fourth constipation and diarrhea and has had since a young adult. I have intermiten abdominal cramps and bloating, my gut seems like i got a BEER belly yet I hardly drink. I too have the back and fouth tedencys in my bowel movements. I usually have a bowel movement once a day but when constipated can go afew days. I also believe I have hemmrohids as i have felt a lump on the out side of my rectum while whipping during a flare up.  I have burning pain about the prostate region when I defecate. Also I frequently pass mucous in my stool. I have had this issue 2 years probably and only 3 times passed any blood (bright red in minimal amounts) and its always passed mixed in with the mucous and seems to follow a bout of constipation. I have been to my family doctor and he says its IBS and I have no real need for further testing. I personally am terrified its cancer or something. I have urinary issues and a sense of burning in the prostate area following defecation. It sometimes is relieved by passing gas. Its almost always relieved if i pass mucous. I don't really understand what can cause this. I have been to a urologist and put on antibiotics for prostatitis. I was on them a long time and wonder if it isn't chronic prostatitis and the antibiotics are killed my stomache, that are doing all of these symptoms. Any one have any ideas or suggestions as to what I should do? I am going in monday to the emergency room so I can try and get a colonosopy done or a swollow able endoscopy done. What would the test be to best rule out cancer or find it if it is. I want to end my worrring about cancer and if its just IBS get on with my life.