Ultrasound at 6w3d shows nothing :(

I had a transvaginal ultrasound performed yesterday. My lmp was dec 15th I got my bfp on Jan 13th and I should have been according to dates 6weeks3days well the doctor saw nothing she said my uterus is thick and she didn't say anything about a gestational sac or anything. She did a blood draw and has me coming in Tuesday and Thursday for further hcg testing. I'm not cramping or anything. But it's very hard to be positive we have been trying for this baby for a year.