How can you stop feeling nostalgic everyday?

It sounds to me like when you say you are nostalgic and think about your childhood every day, you are saying that you felt happier in your childhood or wish you could go back to then because you felt better back then.  If that is the case, I would say it would be a good idea to examine what you feel nostalgic for specifically - was it a sense of being carefree, was it being taken care of by your caregivers, was it that you had a tight-knit group of friends, etc.?  Once you identify what you feel you are missing, perhaps you can begin to rebuild it now. One way to start identifying what you are missing is perhaps to use the dreams that you've been having.  Is there any overlying pattern of the dreams?  Do you see yourself doing the same activities or being with the same people over and over in the dreams?  If so, perhaps it would be helpful to engage in those activities or be with those people.  Or do the dreams revolve around specific feelings?  For example, in the dreams, are you a child being cared for by a parent?  If so, perhaps it is the feeling of being cared for and loved that you miss.  Can you think about ways that you can take care of yourself that make you feel the same way you once did, like engaging in activities that fill up your emotional cup or treating yourself to things. Perhaps even do activities that brought you joy as a child - again, for example, perhaps swinging on swings or enjoying ice cream.  Tailor it to your specific needs.   

You also mentioned suffering from social anxiety disorder - it may be worth examining whether this is new or whether it is something you've always had.  If it is new, what may have caused it to arise recently?  If you've always had it, it may be worth looking into Cognitive Behavioral Therapy (CBT) techniques.