hcg level 86 at 3 weeks and 5 days??

Jane
I need advice as I'm really worrying. I went to the doctor yesterday as I was having mild cramps just a day after getting my positive pregnancy test. Today they called saying they need to repeat my hcg, yesterday at day 27 and 2 days before period was due the level was 86. 
I'm worrying that this is too low?