Blind Ovulation Testing

My bf and I have been ttc for about 2.5 months now. I stopped taking BC pills 8 months ago, an haven't had a period since. I went for blood tests and ultrasounds and everything came out normal (do I should still be able to ovulate).
​I've been tracking my bbt and CM but nothing seems to match. My chart is all over the place and I can't figure out any part of my cycle.
​I've been thinking of taking opk everyday for a month to see what I get.
​Does anyone know of a less expensive way if checking for possible ovulation? 
​In the meantime, we've just been very actively trying! :)