I have a girlfriend. But I keep dreaming about another girl.?

Litarly I have a girlfriend already, been dating for almost 4 months. But At night when I get into the dreaming state of sleep, I have dreams about this other girl.. Now I admit, I did have a crush on her. But Im tall and lanky and not very tan, she liked the big manly looking guys [note: that wern't very manly at all... I Wanna go to school to become a master blacksmith, they wanna hiphop dance? or skate for a living?] anyway Me an my current girlfriend are doing very well. But when I think about this other girl, My back and my arms get all cold feeling, a good feeling. and my current girlfriend. well. Idk I'm not feeling a whole lot of much. am I insane? Is this gonna be another thing where I break up with my current girlfriend. to wait for a girl I can't have? I Do really like my current one. but. These dreams are really starting to bother me. Can someone help of maybe helping me coupe threw these issues before I do something stupid and regrettable?