To anyone that buys OPKs every month, I would highly suggest buying a ferning microscope such as fertile focus. It's a tiny microscope that you put your saliva in in the morning before you eat or drink. You let it dry and look for your ferning pattern. It works similarly to opks because right before you ovulate you have an increase in estrogen. The increase in estrogen increases the salinity of your saliva, resulting in a farming pattern, indicating that you will ovulate soon. The scope is only about $30 which is cheaper than buying opks every month. I just got mine yesterday and I am so excited!