Have You played around with the strap? My sphera hurts in the same spot when I put the strap too high around my head, but when I have the strap lower, it's just perfect.
Also I found that I used to have the strap far too tight, which also didn't feel well. The strap really just needs keep the thing in place, while I used to think that it should press the mask to my face.
If this (or others' suggestions) won't help, You'll just have to try every single one on until You find one that will fit and serve the purpose.
HTH
