I have a breast abscess it was large and painful but has gotten smaller. Should I still see a doctor? Can I die from it if it goes untreated?

Seek treatment . Not likely to cause death, although infection can get in the blood stream if left untreated so would seek medical treatment for medicine and excision as needed. I hope you feel better soon.
Yes, see a doctor. Breast abscess needs medical and many times surgical treatment. Breast infection like any other infection can have serious consequences if it was not properly treated. Please see a health care provider experienced in treating breast conditions.