HCG levels blood

Is anyone here familiar with what’s normal on blood hcg levels? I just turned 4 weeks today. I had blood drawn yesturday at 3 weeks 6 days and I got the results it’s at 33. Which she said is right around where it needs to be but she sounded very hesitant and said to come back Monday to do it again to find out if it’s going higher or not. I’m a little worried now