Empty sac confusion?? Any similar experience?

I went to the doc with light spotting and cramping and was shocked to get a positive test..So she examined me and sent me to the hospital for a scan...Nothing showed up on the screen except an empty sac and the doctor did a inter vag scan..She just said "empty sac" and told me to come back in a week..Im going back friday morning..Im very nervous and dont know how to feel.She said the sac was 5 weeks. It was totally unplanned and it is my ex's baby (if i carry it).. The spotting stopped completely but I still have cramping, more like a sharp pain in the bottom left hand side of my abdomen all the time..That is where the sac showed up on the monitor..any ideas, words of advice..I am so confused..I had a miscarriage at 10 weeks in Feb. Also, does anybody think its odd that i never had HCG levels tested???