Lots of people have some spotting in their pregnancies. It's quite common.

I had some spotting for several days in a row at around 6 weeks. It scared me like crazy, but eventually, after I'd been spotting for several days and no M/C, I started to relax about it. It did just go away: these things happen. I'm currently 27 weeks pregnant and all is well.

I would do your best to stay calm, remember the excellent ultrasound result shows everything is healthy now, and wait for the spotting to end.

Good luck with it.