Storm, sorry you didn't catch this month. Fingers crossed for the next.
Cora, the problem with what they teach in school is that it doesn't take into account the variations between people. In school, I learnt that a luteal phase was 14 days. In fact, that's just an average, and luteal phases can easily be anything from 12-16 days long, depending on the person. I've had luteal phases as short as 10 or 11 days, but unless you know that's a possibility it's easy to get your ov dates wrong.
I was under the care of a recurrent miscarriage clinic when I conceived H, and the only reason they would help me, given my bloods came back negative, was because I showed the consultant my temp chart, which gave her evidence of a luteal phase defect - and at least that was something they could look into. They monitored my cycle, the sonographer spotted a ripe egg and prescribed a trigger shot, and H was born at 41+4.
If you've not tried temping, I'd definitely give it a go. So long as you're pretty regular, it should give you an estimate of your luteal phase length and you can sort things out from there. These days, I'm a regular 26 day cycle with a 12 day luteal phase. And all it costs is a digital thermometer, whereas OPKs can be horribly expensive if you get into them.
JKS - glad they were so nice to you. Hope they help. It reminds me that something called the Oxford Conception Study may still be going. If it is, it's worth joining, as they send you a fertility monitor and a pile of OPKs to use with it. 6 months' supply as I recall. Did it years back when ttc H and it saved me a fortune.
Sorry for rambling post. It's late, it's hot and I can't sleep no matter how knackered I am. Aaaaarrrgggghhhhh!