Does sore breasts occur right before period during pregnancy, or is it consistent throughout the entire pregnancy?

Varies. Pregnant women experience breast tenderness in different ways. For some it is intense. For others not so much. You did not mention if you are actually pregnant or not. If you think you might be pregnant check then check a home pregnancy test. They are cheap, reliable and available at any pharmacy. Do not try and guess at pregnancy based on an unreliable symptom such as breast tenderness.