HCG Levels at 20 and I'm 4 weeks since LMP

Angelina
So I had a blood test on Monday to check HCG levels and it was only 20. The doctor said I should be at least a 100 based on my LMP. I asked the doctor if I'm going to miscarry and he said I might and is sending me to get another blood test Thursday. Any of you ladies have any opinions, advice, success stories, and etc? I don't know what to think and I've been hysterical all day. I know it's not good to be stressed but I can't help it.