Did exercising cause a stitch to spit? And when can I safely resume crossfit/weight lifting exercises?

I had a breast reduction 13 weeks ago. I recovered quickly, began exercising after 7-8 weeks...then 10 weeks...(planks, push ups, light weight lifting, etc) and at 11 weeks after a workout, I had an open wound on my incision line. My surgeon said I spit a stitch. It became infected quickly, I went on antibiotics/silvadine and now it's almost all healed. My questions are 1) did my exercising cause this? 2) Is there some way to restart exercising like I want to and protect my scars/breasts better?