I had my husband look at this and he said asked if you had a water leak. He also said if you had a water leak the sheetrock could be still wet. Sometimes it can take weeks to completely dry. He wants to know if you primed before mudding, looks like you didn't wait for it to dry between coats, and you put it on too heavy.

Wait for it to dry completely, sand it, and see where you stand.

Agree with Sherry Brighton's husband. You probably went too thick and didn't allow time to dry thoroughly.