I'm struggling a little bit with the math. You wrote this post on Oct. 6, 8 days prior to your sexual encounter which would have been 11 days after your last monthly period. I'm coming up with Sept. 17 as the first day of your last period.
If that's true, I'm surprised your period isn't due until Oct. 20.
But either way, you had sex on approximately day 14 of your cycle, which is the perfect timing for pregnancy to occur. So yes, it's very likely that your symptoms are pregnancy related.