A couple thoughts. It's a combined pill, not a pop. So you were unlikely to ovulate while taking it. It's meant to work by suppressing lh and fsh, which means you don't then mature an egg. So it's unusual to get an lh surge while on it, as one of the ways it works is to effectively keep lh down.
Why were you doing opks while taking it?
It may be that your body is now attempting to ovulate, but not succeeding, so your hypothalamus keeps flooding the system with lh?
Another possibility is pcos, but this isn't my first assumption when coming off the pill, as the previous is probably more likely.
Your body isn't ovulating with long term combined pill usage, and so it's unusual to cycling normally. Your body is literally in withdrawal and needs to figure out how to cycle. That's why weird things happen when coming off the pill...
I honestly wouldn't think too much about. I'd also wait until I had at least one period (not withdrawal bleed) until trying to use opks. They're more likely to be giving you 'false' positives as your body might be struggling to ovulate, but you'd still be getting multiple surges.