You know if it's an addiction if you can't do without it and it would cause withdrawal symptoms of some sort when attempting to stray from doing that action for a defined period of time.
Though I don't know how much masturbation precisely is "too much", I will tell you that some people who masturbated excessively has reported that they had problems having sex. They could not ejaculate or cum through vaginal penetration and could only do so by masturbating. This then have caused concerns and problems with the couple's relationship, etc.
This would make sense, as your body has gotten so accustomed through that particular manner of stimulation that anything else just doesn't do the job right.
This is just for your own reference, I am not saying you will have this issue, only that it is a plausible occurrence.