@Mrsbridge17, Aww bless you. I am quite regular but I lack a proper luteal phase length.
Yeah, pretty much is just that. You can take it orally or vaginally, I prefer vaginally as sometimes you may sleep with your mouth open, you have to take the temperature at the same time each morning. It's a bit like monopoly, Don't pass go (go to the toilet), Don't collect £200 (do anything!) until you take your temperature!
A lot of people think that a positive LH strip means they've ovulated and it really doesn't unfortunately, I own a POAS group on FB and the amount of people who say their AF is late and I ask how they tracked ovulation and all they did was OPK's.
The problem is, a positive OPK doesn't indicate you've actually ovulated. Without ovulation, your AF will be either massively delayed or even absent for a month! So it's absolutely critical you temp to confirm you've definitely ovulated. It's also rather handy as if your AF is due and your temperature dips to the cover line (The -------- line on my chart) then its a good indicator that AF is arriving, so it saves you tests...
I've probably made this sound super confusing, but it's pretty easy x