I am 8 weeks pregnant and my hcg is 11000. at 7 weeks it was 3000, at the 7 week ultrasound the dr said he saw nothing. why is it going up?is it viable?

Not sure: If ultrasound is not seeing anything, your physician and you should be concerned about an ectopic/tubal pregnancy. Have they mentioned this to you?

Dates may be off: It is possible that when you thought you were 7 weeks you were actually earlier. Hcg of 3000 would be more consistent with a 4-5 week gestational age. If you were 4-5 weeks at the time of the ultrasound, the gestational sac would not have been visible yet. Hcg of 11000 is also more typical of 5-6 weeks which would be consistent. So yes, could be viable and maybe visible on us now. Good luck!