Bleeding in pregnancy. Yet formed yet?

Hello doctor's , I am pregnant for 7 weeks my last period was 3-07-2016 , and my pregnancy got confirmed on August 12 th and doctor have done ultra sound and found a Sac told me to come after 2 weeks mean while I had my spotting on Aug 18 and bleeding on August 19 th. Bleeding was not as normal menstral bleed but it's just pinkish some times and dark color and had small 2 to 3 clots and bleed was with some sticky mucus with lot bleed during my urination.. My pad was not so heavy with bleed. I rushed to doctor on August 19 she told me to come after 2 weeks as she cannot decide it's complete miss carriage because there's still a Sac found BT this time it's increased to 8.5 MM. And yolk sac and fetal sac not found. Doctor said there's 50-50 chance of my pregnancy. My doubt is am I pregnant or not. If I am pregnant why my yolk sac not yet formed yet ? And why I am bleeding. Kindly answer my question thank you.