This is an old thread, but I still want to share something because I know this is not an isolated case, and someone out there might also struggle to find a solution to this kind of breastfeeding issue. First, not every woman is eligible for breastfeeding, but this is not directly related to breast cancer. You can perform breast screening and diagnosis. You can search YouTube for instructions on how to perform a breast cancer self-examination. You can also visit a breast cancer treatment clinic for a proper diagnosis, such as Nexus Surgical - https://www.nexussurgical.sg/breast-conditions/cancer/ I hope this helps!
Try to pump your breast with hand first or buy an electric breast pump, u can visit any hospital but better the nearest one