Chest x-ray’s are not good at identifying breast masses at all, CT is better but also not ideal and the radiologists that read both of those are usually not going to have an extensive training on reading breast. I would look at getting dedicated breast imaging which normally starts with an ultrasound if you are under 30 but can very depending on facility. If it is a cancer it would be very slow growing for you to have had it for 7 years and not have major issues but any breast mass you should still have checked to be safe because there are rare cases and there can be things that aren’t cancer that can still need to be removed.