Should I be worried?

OK...so obviously I am worried.  I got my lab results from my lab Tuesday when I got to see the heartbeat.  They only did a progesterone test.  Well, the last time I took the test it was 110.  And this time it was 27.4.  Which, I immediately freaked out!  And the nurse assured me it was fine and said the doctor was fine with the results.  So, here is some reason why it could be low.  The day I went to get lab done I had only taken one pill which was from the night before.  I hadn't taken one that morning, because I knew the doctor was going to reduce my dosage that day if everything was OK.  So, should I be worried??  According to the nurse she said that 110 can be a little high and that progesterone does vary during pregnancy.  She said the doctor was pleased with the results and that I should continue with one pill a day.  The doctor told me anything above 20 was good.  But I am so used to having high numbers with this pregnancy.  So, here is what I have thought to keep me sane...my progesterone was 27.4 that morning even when they were showing me the heartbeat.  And the heartbeat was good!  So, that must mean (in my mind) that the progesterone that I have is good.  I don't know though.  It is definately something I will have to talk more about with my doctor.  I'm just praying that everything fine and I am just worrying too much.  But yall please just say an extra prayer for me and this little belly bean.  They are greatly appreciated!!!!