I Can Decide on 1 Position

ok i'm 17 and in love with the girl of my dreams she is so nice and a bad girl in bed we were each others first (as far as sex) but we have a problem during sez i can't stay in 1 position long enough kinda get bored and like every 5 min. switch positions well she asked me yester day why i do this and i said i do not know she said that she almost has an orgasm and then i switch i don't know why but i can't stay in 1 position can you help me please

thanks yours truly joey