I have an ovulation question?

I normally have pretty long cycles, anywere from 36-39 days long. I bought some ovulation tests and took my first test on cycle day 20 and it was positive, me and dh bd that day. I laid with a pillow under my but for like an hour lol. That was the only time we bd around my ovulation time. Does it sound like my days lined up right... Ovulation on cycle day 20 with a long cycle? It seems a little early to ovulate,i did one of those online ovulation calendars and it said i shouldnt ovulate until like the 29th or 30th? Any input would be appreciated :)