Dark circle around the eyes is usually related to sleep deprivation. Lots of reasons for that. Staying up to late playing call of duty for example, or whatever keep you up at night.

I don't know how much porn you watch, but if it is in the hours a day range, then maybe cut back a bit and live some. Personally I just need ten minutes and then I am ready for a nap. That is just me though. If you feel you have a problem with it, there are sex therapist you could talk to. Theu deal with this kind of thing a lot and they can help you determine how much it is affecting your life.