I think sometimes calculating based on LMP may not be accurate esp if you have irregular period, and the implantation could have occured later also. Since the sac is measuring 5 weeks, maybe you're only about 5 weeks pregnant and 5 weeks is too early to detect the fetal pole. I wish you all the best! It's a tough 2 weeks to wait out but no bleeding/sharp cramps is good sign.
All the best to you and hopefully it will be all good for you and your little one. Let's be positive and pray the best. Remember LMP is just estimation. If the scanning shows less than the estimated, only on next few weeks they are able to detect.
thank you my dear
Anonymous