Early scan after ectopic in October

Following an ectopic pregnancy and right tube removed back in October, we were so excited when we found out we are pregnant again. We went for an early scan last Thursday, at around 5 weeks and they couldn't see anything. I was so worried that it was happening all over again. My HCG was only 640, so that explained why they couldn't see anything. I have a scan tomorrow to see if anything is there now, if it's not then this could be another ectopic, I'm so nervous! Has anyone else been in a similar situation?