Arm constantly aching because of pippetting

I work in population genetics, which means I set up 2 96-well plates for qPCR, or do 80 samples for regular PCR almost 6 days out of a week. Recently, I've been getting an ache in my right forearm from constant pipetting. Then I have to go back home and cook, wash dishes and sweep my house, which i do primarily with my right hand. The ache has now travelled to my shoulders and I need to constantly keep stopping while I am working because the pain shoots up. Moreover, my PI wants me to set even more reactions I normally do, because we have like over 160 samples....She is not kind and gets angry if I take even 1 sick day; how do I lessen the load on my arm? Should I start weightlifting at home to build my arm muscles? Has someone done this and seen a change?