HCG Levels Doubling Time

I just found out this week that I am pregnant, on Monday, they did a blood test and found my HCG level at 152.7, then on Wednesday, we did another test, today that came back with an HCG of 228. The doctor wants to test me again tomorrow as well as doing an ultrasound. I am really scared though. I was not even sure I'd ever be able to get pregnant (I've tried off and on naturally for 10 years) and now that I am, I am terrified of losing this baby. I've looked around online and a lot of what I've read says that if I have not doubled in 48 hrs, the prognosis is grim, but then I found a few places that say it may not double for 72 hrs. Has anyone else experienced this so early in a pregnancy and still had good results?

[alaysha]

By 48 hours it should double by at least 80% and by 72 hours it should have doubled completely if not be a little higher. Your levels sound good to me.