bad luck or wrong game??

I have been playing for about six months now both online and live and have had mixed success at best. Initially I obviously had no idea what I was doing but now, after reading many books and gaining much experience I feel like I have a fairly good grasp on the game(by no means am I intending to consider myself an expert). I play only strong starting hands especially in early position and routinely fold when I am certain I am beaten but I find myself continually being drawn out on by inferior hands and beaten by runner runner flush draws and miracle gut shots on the river. Obviously these hands are costing me massive amounts of money because I am attempting to punish those who are trying to make these irrational draws so I am constantly betting and raising when I know I have the best of it-then I find myself making the crying call when the running flush or miracle straight comes through. Any advice as to how I can improve my game and consistently beat these miralce draws???