That is rather common where a sac is observed but nothing viable inside as of yet. Especially at 5 weeks. I also though had severe cramping for the first 8 weeks so I understand where you are coming from with that. I am 11 weeks and just starting to get a bit exited. Once I have my 16 week sonogram I will really celebrate just to be emotionally safe, just in case.
I had my HCg checked again today and just received an email from my dr that' it is within normal range now. I'm having another ultra sound in a couple weeks when I'll be a little over 7 weeks along. I feel like I've been having a hard time getting attached to this pregnancy because of everything.
I was the same exact way, my HCG was low and it was unsure. I fell like we protect ourselves by emotionally pulling back a bit to be safe.