Can you be certain that you are pregnant at 5 weeks?
The short answer is yes. A pregnancy test will be positive, and a transvaginal (internal) ultrasound scan would show a pregnancy sac, yolk sac (the ''feeding reservoir'' for the baby) and possibly a tiny embryo with a flickering heartbeat. If this is difficult to see, as it can be, then a scan after 6 weeks would definitely show these features assuming that your period dates are accurate, and you have a regular cycle.