143bpm fetal heartbeat. 7wks 2days. constant brown spotting since week 4. sound healthy?

Possibly: The fetal heart rate is in the normal range. There is always the chances of miscarriage, but it's great that you are not having heavy bleeding and cramping. I would recommend to just continue to take your prenatal vitamins, exclude intercourse until your spotting has resolved, and follow up with your OB at your next scheduled visit.

Yes: May be secondary to a cervical polyp, cervicitis, or threatened abortion. Need to see OB to verify cause.