Sometimes you can't see the heartbeat that early. It all depends on the baby! I'd maybe wait a week if you can! Then you should beable to see the heartbeat!
I have read some post of women who didn't have a heartbeat yet and they were 6 weeks. I was 6 weeks and 4 days when I had my ultrasound and a heartbeat so if you can wait a little longer do it but if you can't and you go in and don't see a heart beat don't fret go in a a few days to a week and have them look again.
My RE refused to do one until 8weeks, (6 weeks after conception) he said that it is wasteful worry over a heartbeat, imagine if you don't see one, and most likely there is nothing wrong you will be distraut for no reason. I'd try to wait another week! Good luck dear!
i agree wait at least a week bc there are times you can see hb at that age and other times you can not with my first pregnancy i was 6 wks 2 days and we saw a hb but that doesnt always happen. try to wait.