2 positive home pregnancy tests. internal scan done and measured at 3-4 weeks pregnant. could only see ? sac. 10000 hcg. should i worry?

Need more info: At this point you should be under the care of an ob-gyn physician. Don't procrastinate. That person is vital to the health of the fetus and your emotional well being.

Likely no: It would be perfectly normal to see solely a sac at 3-4 weeks of pregnancy. There is a very wide range of 'normal' in regards to HCG levels. It's great that they saw a sac, hopefully they are planning on a follow up ultrasound to see heartbeat? http://americanpregnancy.org/duringpregnancy/hcglevels.html ultrasound is more reliable than HCG for dating. A follow up ultrasound would be good.