Opk help - worrying

I started using opks this month for the first time and I'm a bit confused and worried.

I'm on cycle day 12 and the strips are still almost completely negative (my cycles are usually 25-28 days long). I'm not even close to being halfway positive.

Should I be worrying I don't ovulate?

I'm going to keep going every day (am and pm) and see how I get on but I guess I just wanted other people's experiences and opinions.

Thanks!