Don't get worried just yet Brown blood is just old blood-it is red you have to worry about. If you are measuring 6 weeks 1 day, it is too early to see a HB. Good luck!
ITA!
I went to the OB at what I thought was 6w5d and they saw no heartbeat or fetal pole as well. I also had very bad menstrual cramping. I went back a week later and saw a HB and embryo. A day makes a huge difference in the very beginning!