Dosnt he realize that I will like..eventually move on?

This guy I like and he likes me too and this has been goibg on since january.And he hasnt still asked me out! Hes scared to ask me out cuz he dosnt want us to break up and it takes a long time for him to get to know a person,and alo of his other relantionships didnt last.But he should know by now that im not like the other girls right?He is very nice to me and likes to take couply pictures, we go to alot of places together. I guess hes not embarrsessed of me! And sometimes I feel like he hasnt asked me out yet cuz he wants to see if there is anything better and if there aint he will ask me out.or he just dosnt want to end up lonely..But what I dont get is dosnt he realize that I wont be waiting forever?its like he thinks that I will always be there..Why do some boys do this?? Its like not rlly fair to the girl..