When you have guilt, then any symptom whether it is a cold, a rash or a headache, the first reason you think of is masturbation. Masturbation has no connection with the dark spots are your eyes. The only reason is fatigue and late nights. Now, if you are spending half the night masturbating then you could get dark spots under your eyes.
But, you will agree that this is due to your masturbation habit and not directly due to masturbation. By the way, what do you when you are not masturbating? 5-6 times a week is too much masturbation and should be limited to 2-3 times a week and then too only when you are sexually aroused.
It seems you have become addicted to this habit and you will need to break the habit. Read our answers given in the past on how to break this habit. (You can search for the topic by typing words like masturbation habit in the Box that you see in the top right corner of your screen).