8 weeks and still checking for viability?

Tomorrow I will be 8 weeks and my dr won't confirm viability yet. We did blood and 1st ultrasound and those came back perfect. Last week they did a second ultra sound and they found a small opening in my upper cervix. He said it might be nothing or it might be the start of a miscarriage. I feel fine though - no cramps, no spotting....not quite sure what to think....