soniar, the book Taking Charge Of Your Fertility is very good if you want to understand your body better.
I've never used opks (the ovulation predictor strip things) as I know when I ovulate. It's worth bearing in mind that they don't tell you that you've ovulated, only that they've detected the hormonal surge that precedes ovulation. It's perfectly possible to detect this surge and then not ovulate. Or to have another surge and ovulate later. So yes, have sex again. Having sex every other day throughout your cycle is generally recommended.
If you have sex at the right time, you are young, fit and healthy (same with your partner), your chances of conceiving are no more than 25%. So it's not guaranteed at all and this is why it's normal for it to take 1-2yrs to get pregnant.
I can feel implantation some time between 7-10 days after ovulation usually. Implantation is the fertilised egg burrowing into the womb lining.
There are lots of people on here who use opks. In fact I think there are whole threads devoted to people who chart their cycle if you're looking for likeminded folk.
But the Toni Weschler book I mentioned is excellent. It's stocked in most libraries.