15 weeks with a blood sac half baby's size

In two days time I will be 15 weeks with my little jelly bean. At 10 +3, I had heavy bright red bleeding that I was told was a simple subchorionic hemorage. Two days ago I had to go in for another scan bc they want to keep check on baby as I am high risk. Come to find out that I have what my ob referred to as a sac of blood inside my uterus that she doesn't know what it is. I was referred to a high risk specialist for next week. Along with this she said my placenta's covering my cervix and there is a small chance it may move by its not likely and that a c-section is imminent. I am extremely worried, I had my daughter all natural with preeclampsia and gestational diabetes being the only two risk in that pregnancy. Has any one else experienced this before? Can anyone give me any advice? They told me that my baby is growing great and looks wonderful, just scared these complications could cause me to lose him 😢