Hey hun.
I had bleeding with DD at 6 weeks for about 2 days and with DS for 17 weeks. DD was red blood and DS was a brownish colour but like AF heavy wise. I wouldnt stress( easier said then done) untill you have another u/s.

I really hope all is ok. Good sign is that you had no cramping. It could just be implantation. Thats was the doc said about DD.

Good luck and hope all is well!!