10 wk ultrasound, shadow or possible second?

I was looking at my ultrasound and noticed something that looks similar to a sac underneath it, I’ll circle it in case you can’t see it. Twins don’t run in either of our families so I really don’t know what to think, any help is appreciated! Also noted that I was “suspected” to having multiples because I got a positive test at 3 weeks, but I know this is not an accurate way to determine how many babies.