You would be 5 weeks today
Definitely get in to see a doctor =) Congrats on the pregnancy =)
How frequent are your periods?
For example if you have a 28 day cycle you would be 3 weeks gestation and 5 weeks pregnant.
Or count two weeks back from the day which would have been your expected and thats roughly when you ovulated. That would be your gestation age and if you add on another two weeks that would be your pregnancy stage.
Your DR will send you for a dating scan anyway if you are unsure.
Congratulations on your pregnancy.