Pregnant and estrogen level question

I found out i was pregnant the 4th...we had sex the 19-21 of december so i was only right at 2 weeks when i found out.  My RE did blood work on the 4th and my estrogen level was 67, they took it again on wednesday and it was 114, they took it again friday and it was 196.  The nurse said it isn't going up like they would like so i have to go back tomorrow for more blood work.  I've had some mild cramping but nothing that they don't say is normal.  My question is, is it possible that my estrogen levels aren't going up as fast because i'm soooo early in the pregnancy?  I'm just worried that something may not be right.  Thanks for any input