Breast Pain...HELP!!

Ok so I just recently switched birth control about 3 weeks or so ago. Ever since I switched, my boobs have been KILLING me! I did have unprotected sex during my supposed to be fertile stage. It's now been 9 days since then and I feel like the pain just keeps getting worse. Is there a possibility I could be pregnant? Or is it my birth control as a side effect? Someone please help!! I'm miserable.