I bought a box of ten Clearblue opks tonight. I took the first one by peeing on it for 5 seconds like the instructions said, and didn't even get a control line let alone a test line. I figured maybe I peed too much or too little and so I urinated into a cup and dipped another test into the cup for 20 seconds like the instructions directed. Again, I didn't even get a control line. Am I doing something wrong? This is my first experience testing with Clearblue OPKs.