Is decidual bleeding and then hook effect real?

I got a bfp, followed by AF at 7 days late, and my doc told me id miscarry and pass tissue, it was more like a light or medium light period for 5 days.... Clots but no tissue that he talked about. Now I didn't get a positive opk in November but had 3 day light AF dec 7 -9 and no opk in December yet and no period yet even. The bleeding is also thirty one days apart not 25 like my regular cycle. Wondering if I could still be PG and it was decidual bleeding followed by the hook effect and faint lines or if I just haven't regulated yet.... TIA