Hi E.,
I'm sure you're excited and scared all at the same time. I looked back at your other posts that said that your twins passed on in utero from twin-to-twin transfusion syndrome. :( As devastating as that must be for you, the good news is that TTTTS isn't likely to happen again. Identical twins come from a spontaneous cell division. If the cell divides late, then the twins will be sharing one placenta and one amniotic sac. Genetically, there's no increased likelihood that you will be pregnant with twins again and even less likelihood that you will be carrying twins that share a placenta.
By all means call your doctor, but don't be surprised if they are not too worried about you. While having had a D&C can cause scarring of the uterus, lots of people get pregnant without problems (it seems like you have) and have totally healthy pregnancies.
I won't say not to worry--I think once you've lost babies, it would be hard not to worry (at least for a little while)--but I will recommend seeing a counselor just to give you a scheduled time and space to talk about your grief, your excitement, and your fears in a neutral space so you're not bottling up any feelings. Best of luck in this pregnancy :)