1. If this behaviour makes you at all uncomfortable then its unhealthy to the marriage 2. If your H is doing something in secret that is unhealthy to the marriage its cheating yes...
To use Phil McGraw's words :
If your H wouldn't do it in front of you, its cheating.
-----------------
Questions :
1. Have you TOLD your H you want him to stop consuming porn? 2. Has your husband done this with your knowledge or is he doing it in secret and keeping it from you?
Note : Porn is NOT generally healthy for a marriage, it often leads to internet sex, online affairs, and eventually a physical affair...
It's the mildest step on a dangerous road...
He should stop it if it makes you at all uncomfortable.