Lesley Graham, 42, said the delays may have contributed to the progression of her condition to the terminal stage and is now taking her case to the Ombudsman.
The modern studies teacher, from Rutherglen, South Lanarkshire, found a small lump in her left breast in 2011 and was referred by her GP for an examination by oncology specialists.
But she says it took almost two months for her initial appointment to take place because her case was listed as "urgent" rather than "suspicious".
Although she then underwent a lumpectomy, chemotherapy and radiotherapy treatment, a crucial follow-up appointment was missed. When she saw a specialist five months later, her breast cancer had returned and had spread to her lungs.
Graham, who has a 10-year-old daughter, said: "I cannot change what has happened but I can fight to ensure no-one else goes through this.
"Had I seen someone sooner I do not think I would be in this position today.
"If I had the information I have now about the likelihood of my cancer recurring, I would have demanded a mastectomy as soon as I was diagnosed."
Graham. who is still receiving chemotherapy treatment, added: "Telling your daughter you have terminal cancer is the hardest thing you will ever have to do as a mother.
"I try to stay positive for her sake but some days I am so angry that she has been cheated out of a mother."
An NHS Greater Glasgow and Clyde spokeswoman said: "In this patient's case there were areas where we fell short of the high standards of care and treatment that we strive to deliver to all our patients.
"We have written to the patient to apologise and reassure her that lessons have been learned."