Nervous. Similar stories?

So I went in for my early ultrasound at 8 weeks 6 days since I had a miscarriage last November and only measured 6 weeks 5 days...... there was a heart beat of 122 but this makes no sense as far as last menstrual period starting on June 16th and the positive pregnancy test being on July 5th. Dr. seemed to dismiss my concerns and schedule another ultrasound on Sept. 7th, saying we'll just check again. Now a few days later I have lost two big clumps of cervical mucous and am terrified this means I could be getting ready to lose my baby again...... does anyone have a similar experience that can help me understand? Whether it is good or bad, I would just like to know what is happening.