would you be concerned that these symptoms may be colon cancer?

hi

this website is a great resource, and having had malignant basal cell on my neck at only 30 (diagnosed by myself and fobbed off by doctors until i went and paid privately to see a skin cancer specialist!) i am very aware that signs and symptoms that hang around and can be easily ignored by patient or doctor ,can sometimes turn ominous if not looked into. also my husband had a mildly dysplastic adenonema found in his colon by chance after a doctor sent him to a specialist, which also lead to him hassling his mother to have one (a 20 year survivor or cancer of the appendix after removal and chemo, coincidentally found by chance also after the surgeon removed her appendix while doing a hysterectomy due to having a (sic) hydataform mole)
and in doing so she was found to have a polyp as well, that was not yet cancerous, but well on its way to being...so i really believe in being vigilant...sorry for the rambling...

what leads me to post, is being worried about a friend...
he has symptoms that he has being suffering from for some time, and he and the doctors are just waffling around...i have an urgent sense that i can't shake, that he needs to ask the doctor to check for any signs of bowel cancer...
i don't know all the details but what i know is as follows:
he has suffered from severe constipation for years,to the point he has had to use stool softeners to pass a stool, sometimes only once a week with pain and bleeding.
in the last 3 years, they have switched to pretty much a vegan whole food diet (eating meat only rarely) for health reasons and his stools have improved, although he sometimes has bouts of diarrea and constipation (although he thinks theres nothing worrisome about that)
he has had hemmoroids cauterised before (sorry about the spelling).
he has very low ferritin levels (about 20 i think) which is the first thing that panicked me, as there is not a really good reason for MEN to have really low ferritin, and it sparked the thought to me of long term slow bloodloss from somewhere .he fobs off the ferritin as being normal, because he rides his bike alot and he read on the internet that atheletes can have low ferritin.(but in my view, although he is active enough, he's certainly not an athlete!)
he is UNUSUALLY TIRED all the time, although he gets plenty of sleep (probably due to the ferritin levels) from what he said his hemoglobin is ok, although i don't know the numbers.
he was complaining of getting lymph nodes going up and down periodically in his upper body.
i think he asked about the "c" word once and the doctor said it couldn't be, as if he had cancer of the colon it would be the groin lymph nodes that swell up and not the upper body's.
i think thats daft for the gp to say that!
what if he did in fact have colon cancer that has spread to the lungs?

they think maybe he has an infection, and ran a basic blood test that they said was fine,then sent him for a chest x-ray. he hasn't got results for that yet.

they are expecting a baby in the next week, and i don't want to worry them unduly, but i do know that bowel caner is often not found till too late ans doctors or patients brush off the symptoms, and they have been casually poking around for months and months so far.and he has had years of constipation, etc problems.
i told them casually about my husband and how he had a polyp found that most likely would have turned into cancer if left undiscovered, and how a colonoscopy caught it and dealt with it, and maybe he should ask to have one too, just to rule it out .(my husband had no symtoms however, just a prolapsed mucosa) his wife asked me the other day about my dh, and mentioned that he didn't have any of the symtoms her dh had, and i wanted to say, thats because my husband didn't have bowel cancer, but i'm worried yours might...make him go and get checked and push for it!
but i can't say that, as i'm not a doctor and they have a baby due in a week and i don't want to cause a storm in a tea cup about nothing....but the nagging worry remains...i have casually mentioned about asking for a screening for bowel cancer, just to rule it out and he became a little tetchy...so firstly, do you think there is cause to look for bowel cancer with what i have described, and secondly, how can i gently steer them to confront the idea of looking for possible cancer, without upsetting them too much and having them hate me for suggesting it?
i know some people can't deal with things head on like this, but if it is cancer, and i stay quiet, it may be too late by the time its diagnosed.
members of my husband family have survived cancer/died from cancer, so i do think about it a bit, and don't want my own slight paranoia to take over, but as i said, i got an urgent feeling about it, and i didn't know what else to do, but maybe ask if some others here could guide me, or put my mind at reat with other suggestions of what it may be instead?

thanks for reading my question, and also for sharing your stories and providing a resource that will maybe help others find something at an earlier stage.

K