Question: how many days after your period do you take an ovulation test?
Answer: Day one of the cycle is the first day of your period. Ovulation most likely occurs around day 18. You should get a positive result on an OPK a day or two before that, on day 16 or 17. It's a good idea to start testing every day (or every other day) in the morning a few days before that, around cycle day 13.