Take a break and use your old pair at home. Your eyes need time to adjust, and a buffer of sorts so alternate and SLOWLY increase the time you put on the new paqir.
ALSO consider getting the frame alignment checked.
Zac, seriously, go to your optician/optometrist and get the frame alignment checked. Usually, it takes a few adjustments to get the fit 'just right' before the wearer stops getting headaches.