When did I concive?

So, I stopped taking bc after being on it for almost 3 years on april 16th, and bled very lightly (basically spotted) from april 18th to the 20th. While on birth control I didnt get a period. I started ovulation testing on april 27th. I've been getting high positive ovulation test results since May 6th so on the 11th I decided to take a pregnancy test (also because my boobs are swollen and sore) and its positive! Can anyone give help me understand when I may have concived since I really didnt get a period?