Pregnant but empty sac? Anyone????

Well found out couple days ago i am pregnant, i took four test including this digital. I was having some cramps, so of course i get worried and go to the ER. They drew blood, and did a Ultrasound. The doctor came back and said my levels were 1546 but i have a empty sac. I am guessing by my levels i would be 5 or 6 weeks maybe? Anyways i am upset, and nervous, i have a appointment on the 3rd. Did anyone have any success stories by having a empty sac no fetus at 5 or 6 weeks, i hope i see a lil beno baby at my next Ultrasound!