Fetal tissue test question for those who have done it after MC

So I finally got my HCG test back from Friday and am still at an annoying 15.3 4 weeks post d&c (I was at 8 wks 4 days when I mc) We also send out the tissue to do the genetic fetal tissue testing to give us a better idea why it happened. Our doc hasn't gotten the tissue test results back and we are having a hard time wanting in limbo. How long did it take for you to get the results back if you had this testing done after a MC?? I feel like a month later we should know the results, is this normal or am I just being impaitent?? Between my HCG still being up and and this test taking forever we are going nuts haha. I hate waiting for this stuff, we just want to get everything healthy and start trying again. Ugh I hate when science is being a bitch.