Period a month late, I never cramp but have been the last two days. Breast are also sore and swollen which is unusual. Two negative test 2 weeks ago?

Time for third test! You should consider yourself pregnant unless proven otherwise. Do urine pregnancy test at home and go to your doctor for a blood test for confirmation. Good luck:)
Repeat. Repeat the test to make sure. You may want to get a blood test.
Irregular periods . Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections & hormonal changes can cause spotting. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Schedule a visit.