Just using a conception calendar from the first day of your last period is not much of a method to decide when you got pregnant, unless your periods are 100% predictable and come every 28 days. If they ever vary, you could ovulate pretty much any time in between periods. (Women ovulate about 2 weeks before their next period, no relation to their last period, meaning a woman with 60-day cycles will ovulate on day 46, and a woman who has 22-day cycles will ovulate on day 8.)
Thing to do is get an ultrasound as soon as you can, and ask them for the estimated due date based on the size and development of the embryo only, not on the first day of your last period. (Just tell them your cycles are irregular so you would prefer not to use that date in computing your due date.) Then put your estimated due date into a calculator. It will be able to tell you the difference between the guy in September and the guy in October.
Hi, you are saying
Had sex in mid-September with boyfriend
First day of last period -- September 19
"I came back on Oct. 1-2 and went off"
Had unprotected sex with other guy October 4
"My conception dates was Sept 29 - Oct 7"
"The day I ovulated was Oct 3"
It is a little difficult to help you because I don't know what "I came back on Oct 1-2 and went off" means, and you don't specify how you know what day you ovulated and I really don't know what you are basing the comment "My conception dates was Sept 29 - Oct 7" on. Are you saying you put your period date into a calculator and it told you a fertile window? Or what?
I Meant To Put I Had Unprotected sex Oct 4 sorry