Although you may be exercising ALOT it might not be so problematic, as long as it doesn't interfere with your day to day functioning ie. you can go to work/school/other commitments, socialise etc. When it intereferes with those things, as well as your physical wellbeing, it can be considered a disorder. I suppose it can be considered exessive if it is time consuming, militant, and meaningless ie. you are not training for a specific event or competition; mearly working out to burn calories