If it interferes with your everyday life, it is a problem. Many thing are beneficial, like vitamins and exercise, but you can hurt yourself with excess. If a person is neglecting their personal relationships or job in favour of jerking off, that person has an addiction and it's a problem.
of course it can. anything done habitually can be described as habitual. whether it is medically beneficial or not has nothing to do with it. and yes, there is certainly a point where you're masturbating too much. if it interferes with other aspects of your life, or if you rub the skin off are two examples that come immediately to mind.
It can also take a long time to masturbate.. because for me its hard to get it exactly right, so that its really pleasurable
I don't know your age but I assume that you are fairly young. This feeling may occur from time to time and I believe that many boys will have had it. The answer is to put things into perspective. Firstly try and get involved in other things that use up your energy and take your mind off sex. Secondly, masturbation is a perfectly normal way of releasing the build-up of sexual tension but don't let it take over your life. Think of it like a glass of water - have a drink when you are thirsty.