HCG levels

Hey y'all! I took a pregnancy test last Friday [6.9.17] and it was positive 🎉🎉 I had bloodwork today and my levels were 157, DR said that's not bad, it just means it's early. I'm going back in Friday to make sure my HCG is doubling. What are average levels for early pregnancy? Is there anyway to figure out how far along I am based off my levels? I would guess I'm only a couple weeks. Thanks ladies!