Abnormal bowel movements, colon cancer?????!!!!!?

Ok so for the past 4-5 months i have been having abnormal bowel movements, and when i say abnormal i mean this is coming from a guy who could time when a bowel movement was coming and it was always a helthy amonunt and twice a day!.... but i had changed ALOT of habbits from different jobs, stress of moving alot, finacial things, not eating the way i used to. now i have had periods of constipation, very small stools, lately small stools, after small bowel movement, i still feel unsatisfied, i dont eat healthy anymore, but for the past week ive been trying other things like salads and high fiber breakfast, i only eat twice a day, morning and when i get home from work at 11 pm. i know i dont have healthy meals at all usually what ever im grabing out of the fridge i see, for instance, a can of diced pinapples, make a pbj sandwhich with a high fiber bread and a yogurt.... i know i know...and in the mornins is waffles (2 of them) or just oatmeal, or pb sandwhich... i also work in a bakery/deli/prep food area like a publix. so i nibble here and there on things, sweets, onion rings, cookie. Iam 21, 6'2'' and 220, over the past 2 months i have gain 10-15 pounds.... i also always feel like something is bloking my rectum, i have examined my self (it sucks! dont do it unless you have too) i didnt "feel" any blockage, very smooth, no pain when i was examining around the rectum area, but why am i feeling this way? i checked colon cancer syptoms and i feel like i dont have much in common with the syptoms but just a few things. i get bloated sometimes some sharp pains just below the center of my rib cage, i also have stopped working out as well, ive tried to put more fluids back into my diet, but 4-5 months man? i hope i dont have anything serious to worrie about, if i do i have no health insurance, yet, iam waiting on my 90 day to get it through my work, and dont even make enough to cover all the bills, if it wasnt for the help of my gf. but shes not thinking anything of my syptoms,, and thats another thing, she eats the same way i do and shes fine!?!!? i dont get it,,, please help!