Maybe I'm worrying for nothing?!?

So I had my first ultrasound Sept 29th and it showed just a sac, which it is fine. Had blood test done yesterday Oct 4th and my hCG level came back 5889 (not sure what real meaning is) but that it was good. Then they said they wanted me to come in next Thursday to get an ultrasound. Course I've been so tired I didn't even really think to ask the reason behind that. I hate to say it but last week she had me at 5wks but today she said 5wk.. what the heck??!?!?!?! Idk I'm getting anxious about it. I don't want to be going back in weeks lol, it's already tuff I'm only 6wks and not hearing or seeing baby. lol I'm so tired.