33 years old clear mammo 4 months ago, recently found pea sized lump in breast and chest pain. can mammo be wrong?

Not wrong, not seen: Not every tissue type can be seen on mammography. Up to 10% of cancers may not be seen on mammo and not seen on ultrasound. In this 10%, it used to mean we went right to excisional biopsy. Now, if indicated, you can do an MRI first. Talk to your doctor.

Yes: Mammogram can be wrong -- but also not every lump and bump is a tumor so relax :) talk with your doctor -- if you have a high risk factors for breast ca then do a frequent check with your doctor and self exam -- bad signs include pain, increasing size, swelling, and radiating pain to the armpit of the involved breast.