Could I be pregnant if I had the day the OPK says positive?

My husband and I had unprotected on Sun the18th, as the day went on i noticed sharp twinge in lower left abdomen, which to me signals ovulation. Some months I notice the pain some not, but I usually monitor my Cm better. I did one of the OPK kits later in the day and it was positive. I also created a TCOYF chart today and says I should have ovulated on the 19th based on my last period which was April 3rd. The TCOYF chart says peak day is today, so should I be concerned with pregnancy or not if today is the peak day.