Dreams of groaning signify that your animal instincts are surfacing, and you are unable to contain your feelings, whether they be those of pleasure or pain. Consider the feeling tone.
Islamic Dream Interpretation
Ten Thousand Dream Interpretation
If you are groaning with fear, you will be pleasantly surprised at the turn for better in your affairs, and you may look for pleasant visiting among friends. ... Ten Thousand Dream Interpretation
New American Dream Dictionary
Mystic Dream Book