Womb fluid????

Hi all, had Lucy scanned today (day 27) the vet told me there was def some fluid in the womb but couldn't see anything else as yet, he has invited her back for a second scan a week from today, has anyone else ever had this??
He said another cause for fluid in the womb could be infection!
I am trying my hardest not to get excited about Lucy having fluid but I can help it!!
Over the past few days her teats seem to be slightly enlarged but its quite hard to tell as she is a big dog anyhow (rottweiler) then again I dont know if thats my eyes playing tricks , shes also had creamy odourless discharge, vet says her bladder is free from infection though as she had water infection just after mating. Also over past few days she has started to follow me every where if i go upstairs she comes upstairs even though she knows shes not allowed upstairs!
any info gladly appreciated!!

Usually on a scan if there is a pregnancy to be seen, you see black sacks, fluid filled sacks.

This was my girls scan at 4 weeks (28 days)

all the vet said was that there was fluid in the womb, and that he would need to confirm for def next week