7week Scan empty sac..Any hope?

Just came home from my first dr apt. He did a vaginal u/s and saw an empty sac. I have so many symptoms including nipples that are killing me. No cramps and no bleeding or spotting either. They took a blood test and will call to let me know my HCG number... If low they think there is nothing but if high they will ask me to go in on Sat to get another blood test.  He says my dates could be off but I recorded everything so closely and know what day I had a positive OPK. Has anyone had a similar experience? Do I have any hope?