Upset

So I've had 2 miscarriages. One in feb of 2015 and again last February. First was natural and the last one I ended up needing a D&C at 10 weeks. Just found out I'm pregnant again and I'm 4 weeks 4 days. My dr had me come in for a blood HCG test and it's only at 21. She said that's really low for how far I am. I'm really freaking out and scared I'm gonna lose this one too. Anyone else have a positive story with low HCG levels???? 😭😭