Second little one?

Hey mamas, first of all, congratulations to all of you on your pregnancies!

I had my first ultrasound yesterday at 5 weeks and 5 days because I suddenly started bleeding. On the scan, a second gestational sac was visible with 'something' inside it. The gynecologist couldn't say for sure yet whether it's a twin or if the second 'thing' is just a blood clot (which caused the bleeding). No heartbeat was visible for either yet because I'm so early in the pregnancy. I'm having another scan next week for more clarity. Does anyone have experience with this?