OPK + then - then +. What does this mean?

Cortney • Hi! This is my first month TTC. Im 36 years old.
Hi, this is my first month TTC after being on the pill. I have been using a digital opk to determine my LH surge. On Thursday I got a positive smiley face. I tested again the next day on Friday and it was negative. I tested again today (Saturday) and it was positive again. Please help! Trying to figure out what this means.