How many DPO am I?

These OPKs are killing me. I got my first positives on the 21st and 22nd (CD 14 & 15), and I got another set of positives on the 28th and 29th (CD 21 & 22). On the 29th, I had a positive in the morning, two negatives in the afternoon, and another positive at night. I have NO idea what is going on with me. Any ideas??