Don't be more upset! Really assuming it is a sch, you just have the #1 finding of a first tri u/s that is considered a 'finding'. They just happen. Nothing can prevent them. Really, they are SO common (hence many ob's not stressing over them).
That the bleeding stopped and wasn't major is GREAT!
Really, don't think of risks. Pregnancy in itself has risks and most bad outcomes had zero warnings. There's no way to control an outcome.
All you can do is listen to your body, take it easy (easy to do when we're all exhausted!), and make choices that bring you peace.
I say this as someone who had the worse outcome happen. I lost my baby, I easily could have lost my uterus. There was no way to know I was at risk for anything. If the mamas I know who have lost babies....none saw it coming. That's The Worse outcome that you're thinking of right now and you don't need to. You're in a great spot (sounds crazy doesn't it!?!) You're aware that there's an issue. Most likely it's a sch and you had a minor bleed. There's all sorts of treatments that can help you...taking it easy, bedrest, pelvic rest, watching what you're lifting. Then you have the oppurtunity to check out the status of the issue. The vast majority of the time the sch goes away. Let's say it doesn't...you might end up on bedrest (little to pay for a baby). The risks mentioned earlier are AFTER you pass 24 weeks (viability) and most are even after 32 weeks (viability with little issues with baby's health). So nearly all the time a woman ends up with a baby that's just fine. I'll type it again. A baby that's just fine. Stop thinking about loosing the baby, there's no reason to think you're at risk for that.

This pregnancy thing is so stressful! Go listen to your baby tomorrow and be excited you might get to see the little one! At 12 weeks it's going to be all wiggly and adorable. Get excited to see it!