your staus report won't update for at least two hours, so you might receive credit after that amount of time. Don't sweat it, if you see the message, you got the kill. Early war is pretty easy, so if you are having trouble at that time, it would help to improve your tactics. Also, explosions do not always mean a hit. If fuel economy is an issue, you are cruising too fast.
sounds like you are being "
too agressive"! 
Be more sneaky, act - don't react.