I found out i was preg the end of Oct. On Saturday i start bleeding go to er my Hcg level was 1700 no heart beat was detected i go back two days after my Hcg level went up to 1900 they tell me at that time that ther is a sac but it is empty two days after that i go back and my hcg level is still going up.
I don't know about the irregular shaped sac but I do know that it is very possible not to see the baby for another 3 weeks or so. Some people can see a baby and a heartbeat very clearly very early on. Some people don't. Don't give up hope yet. I'm not sure what the fluctuating HCG levels mean though. Maybe you will get a more helpful post. You may also want to try to search it on the net.