Opk reading

My cycle is 30 days long and regular. I had an  adoration 3 months before and again on TTC from last month for my first baby.

 I got positive result for 2 consecutive days on opk Then it was back to - tv again .

  when intercource is more imp ? within positive opk  OR positive opk plus next 12 to 48 hr ( result may be negetive on opk)