hello, if urs is only 4th week pregnancy, think still early to see anything in the scan.
cos i was also like you (kiasu) LOL! the moment I test the kit with positive, I went to my gynae on the same day and gynae didnt see anything in my womb and keep ask if i'm sure i see a + on the kit.
but after minutes of scan, she spotted a super mini waterbag which was around 3mm only. I was told that i was in about 4week+ to 5week pregnancy
dont wry, if you're really pregnant you'll get to see the waterbag on the 5th week onwards... =)