Hi Melanie
my heart goes out to you how awful to wait for two weeks for another scan. did they do a blood test to check the levels. also what type of scan did the do the normal one or an internal one.was it a good scanning machine..
some times a heart beat will not show up at 7 weeks for may reasons,
type of scan that was used, although you are 7 weeks by your last period on less you are positive on what day you ov the baby could be a few days younger and thats why its not showing now . some times it doesn't show they like to keep us guessing,
so don't give up yet and try to relax and think positive thoughts.

Have you been having any morning sickness or any other symptoms, how come you had a scan at 7 weeks if you don't mind me asking.
I hope it all works out for you let me know how your getting on
naimh