All is not lost!!! See whether you can get the extra two repeats from the other half of the fabric, as amma suggested. If not, perhaps you can buy a bit more of the same fabric to get the extra two repeats?
Assuming you can get your six repeats in some way, using hexagons from two different fabrics could make for an awesome OBW quilt.
And if were to find yourself left with just four repeats after all, there are tons of other options. Make four-patch posies perhaps; or you could also consider making kaleidoscope blocks into a different kind of OBW (4+4 repeats in the octagons, and 4 small triangles in the small squares). If you combine the pieces cleverly, it would make for a wonderful look.