Breast issues and anxiety?!

Okay SO I have been to my doctor and she keeps telling me not to worry, but I’m worried. I am 22, and 3 years ago I began BC with a triphasic bc pill. After 2 1/2 years on it it started to disagree with my body. My left breast began getting sharp pains, ( rarely the right) and during the last month on it, my left nipple had milky discharge for 2 days and intense left breast pain. I had a physical exam and the doc felt nothing. I switched pills and the discharge left but I still get sharp left breast pain on and off.. doc still feels no lumps? Should I worry? Why is it dominant in the left? I can’t help but feel like something is wrong!