Being that you realize the experience that you are going through and based on the information that you have given "I have tried stuff..like letting her catch me jacking off" I am going to suggest that you find a therapist, preferably one that is experienced is sexual issues...
Since nothing has occurred up to this point other than fantasizing on your behalf you are one step ahead of the problem already. My concern is that when a person begins to engage in fantasies such as the one you have describe...the fantasies become more frequent and intense.
It also appears that you may have entered phase two of what I am discussing in that you have placed yourself in the position that your mother might catch you masturbating. This means that you are seeking ways to make your fantasy come to life and indicates that the initial phase of the fantasy cycle is no longer rewarding to you.
Fantasies actually become a part of the person's being when the are repetitious. This is why we encourage people to view themselves or fantasize about them self in successful life and business situations. They act as a motivator for action in reaching life goals.
The problem part ot this is that when the fantasy is unhealthy, they still become a part of the person when they are repetitive and they also act as a motivator for action in order that they are brought to life.
Realizing that the fantasy that you are having is unhealthy, holding on to it to the point of making it real and bringing it to life would take your good person and leave him standing in the shoes of a criminal. The need for satisfaction compulses one to act on their feelings...in your situation it may not be your mother but another female and for the purpose of relieving the physical body of the anxiety that has been heightened the result of the obsessive thought.
With this, I am going to suggest that you seek out a therapist that specializes in Obsessive Compulsive Disorders. A good therapist will help you understand how your fantasies began and how to stop them before it is to late.
Though I do not know you personally, I do know that something occurred in your life that triggered the onset of the fantasy that you are having for they were not with you at birth.
I sincerely ***** ***** you decide to be a proactive part in your own help and enter therapy. I believe that because you have come here with your thoughts this is really your way of seeking help because you realize that they are not right.
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