1st ultrasound at 5 weeks

I have a question about measurements. I went in last Friday (Dec. 5th) for my first ultrasound. According to my LMP I thought I should have been 5 wks 1 day. The tech said the gestational sac was only measuring 4-4 1/2 weeks, but that it looked good. My HCG levels are more than doubling every 2 days as well. I guess I am a little confused. My boyfriend and I had sex on Nov. 14th and 15th, and then approximately two weeks later on Thanksgiving I had BFP. We have not had sex since that weekend so know I had to ovulate sometime around then. I guess my question is should I be worried?? My doctor said everything is fine and I am scheduled to go back for another u/s on Dec. 17th to see a heartbeat. Is that too soon considering I am measuring almost a week behind? As of Dec. 8th my HCG levels were 7200. Any advice would be great!

[krushing]

If the doctor isn't concerned, then I wouldn't be either.  If your levels are rising like they should be and you had a good looking sac, then I would just wait until the next ultrasound.  It very well could be you ovulated later than you thought and that is why you are week behind.  Good luck!

[Darkestlight]

I wouldnt worry yet. It's still very early and a u/s has the possibility to be +/- 5 days. My baby is measuring 5 days behind but still very healthy. I wouldnt worry.  It should be possible to see a hb on the 17th... even going by what u measure you would be around 6wks which is in good range for a first hb sighting.

[clairelou88]

i wouldnt worry about it, when i had my first u/s my midwife gave me my due date which made me 10w 3d and when i went for u/s i was told 10weeks, but it doesnt really matter that it was 3days out, everything is still fine :) i agree with krushing prob ovualted later.