OPK Help please??

Jennifer

I'm really struggling with these OPKs. My cycles aren't regular so I started testing on cd 7 just because I wasn't really sure. Well now I'm predicted to be ovulating tomorrow and I haven't gotten a positive OPK yet so obviously that prediction is wrong. But I'm getting really frustrated and disappointed because the tests just aren't changing at all... am I doing something wrong or is it just that I won't see any changes until I get a positive?