Abnormal ovulation?

I posted earlier in the week about the Clear blue easy digital advanced OPK. Only two days after my period stopped I went from low to peak ovulation over night. I guess that is possible?  Well that was Wednesay and its Saturday morning and I bought a completely new kit and it says peak ovulation after it said low ovulation yesterday? Neither of these time frames are close to what Glow has predicted for my ovulation time.... Is this accurate? I'm afraid I'm going to miss my ovulation all together! Please help!