K.F.
First, I'm very sorry. I've has 3 miscarriages in between my first daughter and my twin daughter and son, and I think my periods returned about a month after each loss.
I'm sure it varies, but go ahead and call your dr, that's what they get paid for. You may have to have your hCG level tested.
I remember getting blood tests after each one to test for hCG levels (what home preg test detect) to determine if the preg was completely disappearing. I guess the menstrual cycle will not resume until every last tiny cell/remnant is gone. I suppose how late into your preg also is a factor. Normally, the hCG gradually goes down.
Make sure you have at least one supportive person that lets you express your feelings! Hearing things like "Be happy you already have a child." "You can try again." "It wasn't meant to be." don't really help, do they? Your loss matters and so does your grief.
Peace,
K.