This has been debated at various times on the AB -
one thread that runs through the debates is the difference in approach to pronography between men and women as individual genders - obviously there are many exceptions on both sides but -
the general concensus is that men enjoy pornography even when involved in a fulfilling relationship, and women find that a strange outlook to have.
From a man's perspective - masturbation is an entirely selfish self-centred act, and perfectly normal. Pornography is an ejoyable stimulation to masturbation, and can be enjoyed as a solitary activity by a man - pleasure for its own sake.
That is a world away from sexual activity with another person, when needs and considerations are paramount - an entirely different experience.
Therefore it is perfectly possible for man to be in love with, and sexually satisfied by his partner, but still enjoy the solitary 'no pressure' activity of watching porn and masturbating.
So, as far as possible, I would consider this a 'normal' activity - unless it upsets you, when the whole issue shifts to new ground.
I would not, however, class it as a 'hobby'!