What is wrong with my ollie?

everytime i do an ollie, the board kinda tips sideward, so when i land it, its either i fall or i lose speed and turn the wrong direction. im doin all the steps which are pop, slide and get my back off up right after popping the tail. but somethings really wrong.. is it bec im sliding it the wrong way? or does the grip tape have to do with my ollie?