So, how do ya'll keep track of your cycles, predict when AF is due, when you're fertile, etc.?

I've had my panties in a bit of a knot this past week because, according to Glow, AF was due a week ago & no BFP in site. My period has been like clockwork up until this year & has now become irregular, which is why I've started tracking (plus TTC of course).

Looking through my calendar today I noticed that I had logged a couple days of spotting in April as a period, which it wasn't, & I'd meant to remove it but forgot until now. I deleted it, & that then changed my fertile week & AF estimation for June, which would make me only 2 days late now as opposed to 6 or so.

I guess I hadn't realized how easily the predictions on here can change, so I've probably been putting a bit too much stock in it. I'm wondering what other methods, if any, people use for tracking things? BBT? OPKs? Common sense? I use OPKs but I wish there was a test that would tell me when my period was due so my next cycle can start! Haha