Dear Raven,
Your most likely to have your ovulation on day 11 since you have a short cycle. if you count ten days from the first day of your last period you land on sept 20th, which means that you probably got pregnant from having sex with your husband on the 19th.
Your fertile for 6 days till your ovulation, so sex between september 14th and september 20th would have gotten you pregnant. 21st of september IF you have a late ovulation.
I think there is no way you could have gotten pregnant from sex on oktober 2nd since your ovulation was more then a week before.