Not at all, masturbation is healthy. However, if youre a guy at least, it can start to hurt if you do it too much so if it does, take a few days off to let it heal. Sometimes the shaft of your penis just cant take all that friction and rubbing and the veins start to swell and it can be painful. Or better yet, try to keep yourself to twice maximum if youre doing it EVERY day.
But for your question, theres really not a number for "Too much" masturbation. As long as its not interfering with your life, do it as much as you please. Its good to explore yourself like that when youre young.