It certainly is possible. And until this cycle when I am trying a different OPK, I personally had NEVER seen anything resembling a second line on a OPK.

Remember too that we don't necessarily ovulate on the same days each cycle. Many things can affect our cycles, even things which we aren't aware of, or which we don't believe affect us personally.

You can also show all of the signs of leading up to O, including + OPK's and STILL not actually pop the egg.

Hang in there.

Lisa