It is common to dream about houses. They usually symbolize our emotional and psychological selves. All of your experiences, stages of development, and parts of your conscious and subconscious life may be represented by that house. The house may be representing issues concerning a particular dilemma in your life, or it may be more general and comprehensive.

That your house is always in different shapes and sizes, represents the fluctuations or instabilities you are feeling in your conscious, and subconscious, life.

Finding extra rooms suggests the recognition, or discovery of previously unnoticed aspests, abilities, fears, or traits in yourself. If the discovery is distressing, this may reflect a change in your current state of affairs that is distressing in your waking life.
Being that they were in a separate wing, suggests you felt that whatever situation is happening, or issue you have, wasn't directly affecting you, or could be ignored.
Now that the rooms are now 'connected' directly to the main house, suggests that you feel you are being directly affected by the situation, or issue, and it is no longer possible to ignore it. That you must face your dilemma head-on.

Being haunted - represents memories, feelings, or guilt that may haunt us. Parts of the wider awareness of the subconscious that attempts to communicate, the 'husks' or influences from past traumas or events that have been emptied of actual hurt and real influence, but still have the ability to affect us as habit patterns, fantasies, hopes, or longings we have given time to, but are now entering back to the present.
That it is a sinister spectre, suggests it is a bad experience, emotion, feeling, or habit from the past that you thought your were rid of....but is now re-appearing for some reason. And these 'new rooms' are re-opening the past, or are reminding you of something unhappy that happened long-ago.

Downstairs:
First floor(if this is how you describe the ground floor) symbolizes practical everyday life, sexuality, and the hips and legs.
First floor(if this is how you describe the floor above the ground floor) symbolizes internal needs, rest, sleep, and the main trunk of the body.
Basement - symbolizes the deepest part of your unconscious mind, your foundation(The beliefs, and ideas, that were 'built' in your earliest beginnings).

The ghost is a boy - If you are female and dream that you see a boy, it indicates that you are developing or recognizing the masculine aspects of the figure in your dream. Alternatively, it may represent your feelings about a real-life boy who is important and significant to you. Your motherly instincts may be taking over.
Alternatively, it can symbolize the immature aspects of yourself that still needs to grow. Your inner child may be trying to draw your attention to parts of yourself that you need to recognize and acknowledge.
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Is there a situation, or issue, you are dealing with that is dredging up old, possibly hurtful, memories or feelings?
Are you facing a situation, or problem, which you feel has practically no solution?
Do you have a 'darker' side of you(anger, depression, etc) that you are repressing, or darker thoughts that you buried long ago?
Is there something from your past, that you may be ashamed of, or feel guilty about, and it is now possibly re-surfacing?

Because this is a recurring dream, suggests something from the past....and is also of importance to you.
Hope this helps you gain some insight.
Good luck!