I'm sorry that you feel alone and for your loss.
What are you calling the ER and OBGYN for? Do you need medical help or are you just calling to ask them why you miscarried?
If you are asking them why you miscarried, unfortunately I don't think you will get any answers. First miscarriages are almost NEVER investigated and if you already have had two healthy pregnancies they are probably even less concerned about a "problem". I don't know how far along you were, but most first tri miscarriages are caused by chromosomal abnormalities...nothing you can prevent or cause. Since chromosomal abnormalities are so common, doctors just chalk up most first-time, first tri miscarriages to them.
I'm sorry you're going through this. I know how tough it is not to have a concrete answer.