I'm so sorry for your loss - it's cruel and unfortunate that drs don't start testing until losses become recurrent. It doesn't take away your pain and doesn't give any answers.
I see you are in USA? Can you see your PCP and ask for tests for clotting disorders - some of the symptoms for these are heavy periods and easy bruising. I also know of someone whose PCP has her thyroid levels checked every year - the reason for insurance purposes is 'weight gain' - she does have a family member with thryroid problems. Also ask if you can have the test for 'lupus' this is an autoimmune problem that can cause miscarriage.
Good luck!