Most everyone has said it. You attract these types of individuals to you. You may not mean to but you do. Maybe you could work on being a little more selective. I'm not saying you're not now but look closer at the type of boy you're dating and see if there is a common thread then stay away from that.
Best advice really is top do the complete opposite of what everyone tells you. Except for me that is, otherwise you'd be back to doing what everyone tells you