in order to guess at an appropriate answer, you have to know the date that you ovulate. Sometimes women ovulate anywhere from day 11 to day 15, 16. To know the true date, you have to know what how long your Luteal Phase is as well. If on the 15th, that is day 12 for you, and the rest of the days is day 13,14 & 15 of your menstrual cycle- right smack in the middle of when ovulation can occur. If we generalize, a 32 day cycle would mean that if you ovulated on the 12th day (feb 15) you would have a Luteal Phase of 20days, which seems improbable. Because a LP should last anywhere from 12-18 days. Id go that you conceived on day 15.
but that is just me. if i confused you im sorry, but fertility is math, and it requires a lot more thorough info than wha tyou have provided.
good luck.