relationship problems

A month ago my boyfriend got diagnosed with testicular cancer and the doctors said that his chemo would affect his mood swings but lately he's been getting a little physical and started calling me stupid and dumb for no reason. Today he grabbed my thigh really hard and bruised it all because I didn't answer him fast enough( I was falling asleep in the car at the time).I don't know what to do I feel like it's because of the chemo but I don't know anymore