Can 2 months of serious anxiety can become the cause of health issues such as , digestive problems and oral cankers or it is sign of colon anal cancers?

Yes and yes: Aphthous stomatitis involving the common canker sore can occur in up to 15% of americans, and may involve some bacteria like staph epidermidis. However, similar-appearing aphthous ulcers can be seen with herpes, crohn's disease, and other systemic disorders, you are appropriately concerned about your health--please consult a local physician for evaluation ; targeted treatment, as needed.

Serious anxiety: Serious anxiety can definitely be associated with digestive problems and canker sores. At 23, it's unlikely that you have colon or anal cancer, but in your other info you've written that you have "black terrible stool" at times. I suggest letting your physician investigate this so that anything potentially problematic is taken care of. Referrals can also be made for help with anxiety. Be well.