Technically by the time you conceive you're "3 weeks" pregnant, so at one week you're still having your period or whatever lol. The first two "weeks" are menstruation and ovulation. If you're going from one week after conception that puts you at like 4 weeks. I tested positive at 4 weeks. I was very tired and my breasts felt like they were on FIRE. So yes, sometimes you can have symptoms a week after conception, but it's also common to not have symptoms until much later. :)