What to do next

I have had four miscarriages. All early, none grew past six weeks though I carried the third and fourth for eight and twelve weeks. Thanks to progesterone. We have had all the testing for clotting disorders, endocrine disorders, the antiphospholipid. We also had the hysterosapilingogram and have both had karyotype done and everything came back normal. The doctor said it looks like bad luck. He said to take a low dose aspirin everyday and call him when I get a positive pregnancy test. I don’t have any children. It seems like something has to be wrong. I’m afraid to keep trying with the same result. Is there something else we could do? The doctor seems like he knows what he is doing four just seems like a lot if there isn’t another problem behind all of it.