I have been having sore and heavy breasts, periods every other month and cramping what could be causing it? could it be gastrointestinal or a cyst?

3 issues: Breast pain, pelvic pain and irregular periods may or may not be related. Each has a very long list of potential causes that is beyond the scope of a simple answer. The next step is to schedule a visit with an Obgyn or a virtual visit on Healthtap to help narrow down the potential causes and help guide you through the evaluation process. If you think you might be pregnant check then check a test.