Hi, My Left Side Breast Hurts, By My Armpit. It

Hi, my left side breast hurts, by my armpit. It feels like it's my breast muscle. I don't know. I don't feel a lump.
I felt some discomfort 2 weeks ago when my BF laid on my chest and I had to pull him off, and the last 3 days it feels like it's getting worse to point where I am having a hard time steering my car wheel.
Thank you,
Eve