If you were 5wks and 5 days on sept 21 when did get pregnant?

To calculate the date of conception, we need to subtract the number of weeks and days from the date given.

Given date: September 21st (5 weeks and 5 days)

5 weeks = 5 x 7 = 35 days

5 days = 5 days

Total number of days: 35 + 5 = 40 days

Now, we subtract 40 days from September 21st to find the date of conception:

September 21st - 40 days = August 12th

Therefore, the date of conception is August 12th.