First, Congrats!!! I'm happy and excited for you. Wowza, that is a super high hcg! Being so high could mean that perhaps you have your dating wrong? Is that a possibility that you are further along than you think? And yes, it could also indicate twins or triplets! Unfortunately, there is one complication that a super high HCG level can indicate which is a molar pregnancy. When is your next doctor's appointment?! I'll be interested in what the doctor has to say! Let us know!!
Like specialmom said, there are a ton of reasons for high HCG- one is definitely twins. Sometimes you can have a period while pregnant- so it's also possible that you are further along. Are you getting an ultrasound done anytime soon? That will help with dating and confirm if there is more than one in there- of course you will likely need to wait a few more weeks if they suspect you are only five weeks a long- there isn't much to see on ultrasound at that point.
Keep us updated and congratulations!