6 weeks postpartum follow up

Has anyone had who had a loss, had there doctor say that you have antibodies but it’s very low so it didn’t cause your loss? Today I had a follow up appointment after my loss(stillborn) and my doctor said that they can figure what cause my baby to have no heart beat. She’s not sure if my antibodies caused it but they aren’t sure cause it doesn’t show in her blood. My doctor said my antibodies only show when it’s dried up or when my blood is cold. However it doesn’t show when it’s warm. She doesn’t know why it’s like that. She said I don’t need a shot or any medicine because the antibodies only show when it’s cold. I just think it’s weird how she can’t really determine why it does it or what cause my baby to be sleeping. I’m scared if I get pregnant if I’ll lose another baby..