Brown spotting @ 7wks+6

I've had brown spotting on and off since about 5 weeks. I had an ultrasound on the 11th of this month and the Doctor said everything looks fine. We even heard the HB, it was at 120 BPM at that time ( 6wks+5). However tonight the spotting started again and was a bit heavier this time. Has anyone else had this issue? I had a MC back in October and I'm trying VERY hard to stay positive, but it's hard not to worry in this situation.