Recurrent pregnancy loss with IVF-

Had testing done after my second miscarriage. All numbers were great with my second transfer, beta was rising and everything was great! 24 hours after my last beta I had a miscarriage. We are going into our 3rd attempt with a transfer and they did all the bloodwork on me and can’t find anything. Only thing they found was my thyroid was 4.5. I am on Synthroid and now it’s back down to 2.2. Anyone have similar thing happen and have a baby??? I am losing hope! I am hoping it was the thyroid and we got it fixed.