Help please!

I have been charting my bbt this month and everything looks pretty normal. I had read somewhere that opks can be used to measure hormone levels in pregnancy as well as for ovulation. Today is cd34. I am supposed to get my af tomorrow and decided to take an opk test a few minutes ago. When I wiped I saw a very light pink stain on the tp, but then was thrown off by the opk. I use the clearblue digital and it came out as high/peak with a solid smiley face. Can anyone give me an explanation?!​