Reading your story it seems to me that these issues arise after you stop eating fibre. It ends up with you having rock hard stools and some constipation. I don't believe that tumours can come and go like your lump does so it doesn't sound like cancer based on your description, but I'm not a doctor. You may have caused an anal fissure or small tear, these can be painful and can take some time to heal. The key is to keep that stool soft so the tissue can repair itself over time. Keep things moving with fibre and fluids. You have to take a disciplined approach to this or it seems to me the problems and pain will just come back.
From the 'net:
"A diet with enough fiber (20 to 35 grams each day) helps the body form soft, bulky stool. A doctor or dietitian can help plan an appropriate diet. High-fiber foods include beans, whole grains and bran cereals, fresh fruits, and vegetables such as asparagus, brussels sprouts, cabbage, and carrots. For people prone to constipation, limiting foods that have little or no fiber, such as ice cream, cheese, meat, and processed foods, is also important.
Other changes that may help treat and prevent constipation include drinking enough water and other liquids, such as fruit and vegetable juices and clear soups, so as not to become dehydrated, engaging in daily exercise, and reserving enough time to have a bowel movement. In addition, the urge to have a bowel movement should not be ignored.
You can also try - Bulk-forming laxatives. They generally are considered the safest, but they can interfere with absorption of some medicines. These laxatives, also known as fiber supplements, are taken with water. They absorb water in the intestine and make the stool softer. Brand names include Metamucil, Fiberall, Citrucel, Konsyl, and Serutan. These agents must be taken with water or they can cause obstruction. Many people also report no relief after taking bulking agents and suffer from a worsening in bloating and abdominal pain."
Try to keep that stool soft in the meantime and if it doesn't get better you may need to bite the financial bullet and see a doctor for more investigation. A colonoscopy or flexible sigmoidoscopy would be a way to get more information if you are really worried.
I would try a stool softener like Miralax which is OTC and non-addictive. You may have to play around with the dosage but it works very well. I hope this helps and best wishes.
If this was caused by colon cancer, you would have found out a long time ago. Colon tumours spread and grow really fast, especially in the colon where new cells are always being shed at a faster rate compared to other areas of the body. Without treatment, you wouldn't have survived for very long. I don't think what you have is cancer.
I'm not a doctor, but this just sounds like a case of severe constipation to me. In your case, the bleeding must be caused by hemorrhoids or anal fissures, which were bound to show up sooner or later judging by how hard you've been straining.
Both hemorrhoids and anal fissures can become a chronic issue. They won't heal until your constipation is completely alleviated.