I was just wondering if anyone knew what fluid on the outside of my uterus could mean?

I found out I was pregnant yesterday, so the doctor wanted to send me for an US today. He wanted to send me for one as I had a mc (blighted ovum) mid July and hadn't gotten AF back before we fell preg again. There was a sac measuring 0.5 mm (which could only be seen via internal scan) and there was a substantial amount of fluid just outside my uterus.

After last time I am a little worried, so if anyone has any advice/info etc that would be great.