Hiya
I did an OPK on CD12 and it was a +ve and as I had never had a positive before on an OPK it seemed odd - I did not get my +ve on HPT until CD17 (and it was very faint).

Good luck - I think it can be a sign but you should definitely wait for the HPT +ve before getting too excited as I don't know how reliable they really are.

T.