Miscarriage issues

Has anyone been going through many miscarriages and doctors not knowing what the reason is ? We have been trying for 3 years now and I’ve had 4 miscarriages and currently pregnant with the 5th and my levels not looking too good , anyone have any idea what keeps going on with me ? Anyone experienced anything like this ? I don’t have an issue getting pregnant I’m having an issue keeping the baby …. Anyone have any suggestions as to what’s going on or any tips of what to do ? Cuz I don’t think I could live through a 5th miscarriage…