Low hcg

So I took a pregnancy test this morning and it was positive (whoohoo!). This was my first month with our fertility specialist because of pcos. I went in for a blood test. today is two weeks after I conceived exactly. They said that I am pregnant but my levels are a little lower. My level was 33. I've read a lot that it's common for women to have a wide range of levels. Has anyone had a similar experience. I go back in on Thursday to get another blood test in the hope my levels have doubled! It's still pretty early on and I know most people don't get blood tests at 4 weeks. Just praying it isn't a chemical pregnancy!