By now the cardiac activity should have been noted. However, if the sonologist is not experienced or the machine is not good, the heartbeat may be missed out. Please get a scan done by an experienced sonologist and get a transvaginal scan done (which shows up the cardiac activity better than transabdominal scan, and also rules out ectopic pregnancy better). If the heartbeat is still not seen, then it is advisable to get a serum test for beta HCG. This will give some light on state of pregnancy. It is no point taking the medication prescribed if heartbeat is seen on TVS or it is absent.