Tests?

I’ve just had my 3rd miscarriage this month. 1 chemical, 1 missed miscarriage and one where I started bleeding, seen our babies little heartbeat and miscarried the next day. I feel like I’ve hit a brick wall! The doctor has said until I’ve 6/7 miscarriages they refuse to do any further testing. I’m in the UK and they don’t even try progesterone. I have an under active thyroid which was balanced when I fell pregnant after begging for tests while pregnant I was really under and by then it was too late. Is there any testing I can ask before I start ttc again?