please help I need to vent

I'm 29 years old and I have two kids one is 2 , one is 4 but 4 year old was born early and was in nicu and my 2 year old was an emergency c section because his heart rate dropped ! But other wise today there very healthy ! I am on my third pregnancy a little girl and today I got a phone call with my first experience and with my husband being deployed and being in an area where I am completely alone I'm very broken hearted today and I wanted to know if anyone had this same problem and how there births turned out! So at 20 weeks I had my anatomy ultra sound , today I am 22 weeks and got a phone call about that ultra sound saying that the baby is fine but they saw brightening of the stool which I guess she said could be a possible sign for Down syndrome   ! I know no matter what happens I will always love my daughter I wanted her more than anything on this earth all my kids I did ! I'm scared that if this is true I will be a bad mom since I don't have patience now with my two little ones ! I'm scared to death and I feel so alone right now ! Please if this has happened to you please share your experiences !