Please Help!

So im really freaking out right now. My husband and I have been TTC. Well last week i took a test and it was negative, the next day, the first day of my missed period, i tested again and it was positive. Never got my period or even any spotting. Well last night i started to bleed really heavy. I called the dr today and had an ultrasound. They couldn't find a baby but said it may be too early too tell but also said i recently had a cyst burst. They did blood work and said my levels were at 1800 which would indicate a very early pregnancy. I go back Wednesday for more blood work and they said if its doubled then that is a good sign i will go on to have a healthy pregnancy. Has anyone gone through some thing similar? I am feeling so lost. :(