Anxiety and Grief - Buried Alive thoughts

Hello, I suffer from anxiety and take diazepam sometimes, it's not really bad bad anxiety but i do have recurring thoughts that kinda torture me.

The day we buried my mother i started having these thoughts, about "what if she wasn't dead and we were burying her alive?" I opened the casket and saw that she was dead.

Yesterday it happened again, this thought of what if she was alive and we buried her alive, she died at home but her heart stopped and she had rigor mortis, her blood settled and all. The next day when we buried her and I saw her in the box, she was still in the same position.

Has this hapenned to anyone of you who has also suffered grief mixed with anxiety? or am i going cray cray?