Miscarriage

Hello…
My name is Claire…I’ve had 3 pregnancy losses ..one was at 6weeks and the rest were chemical pregnancies they exited even before I noticed I was pregnant..my gyna did thyroid.. diabetes and immune disorder test with my blood and found nothing …but my BMI is 35….am confused and traumatized…what kind of advise would u give…what should I do next I really wanna conceive but this time successfully..but am full of fear..what could be the cause of my miscarriages?…can I try and succeed next time…?..what’s your prediction what could be the cause?….please advise on how or what I can do to carry successfully to term next time I try