Aussie ladies- OPK help please!

Ana
Hi ladies, I'm trying to find a cheaper alternative to ovulation kits and hoping for some suggestions. I love the digital one I have been using as it takes all the guess work out of it but very expensive. I've also looked at the first response ones (non-digital) but still quite expensive. I've spent SO much money on TTC! Any suggestions would be great, thank you 😊