Read mind blown

So today I went in for my ultrasound expecting to hear it's not going to be a viable pregnancy and now my head is spinning. Last week they saw a twin pregnancy one with something just looking like cells and one empty. I got today and they are now seeing new developments like a new pregnancy. A normal yolk sac and a fetal pole but no heart beat. The doctor told me in very very rare cases an egg can be fertilized later on. any one have this happen? And have a normal pregnancy? Doctor doesn't want me to terminate because something weird is going on, and there's a small chance. If my hcg level is rising like last week it's even more of a mystery.