Could I have torn inside stitches from my breast reduction surgery? What happens if I did?

At 2 1/2 weeks post- op I did some light housework but I lifted something heavier than I should have for a few minutes. Later that day my left breast starting hurting some. The next day , it seemed a little better. Now 5 days later, it definitely aches quite a bit. I have no pain in my right breast. I It doesn't ache constantly but it does hurt more if I move. I walk around my block and that usually feels good. Now that causes pain in left breast. I am terrified about what may be wrong.