OP - you are right to feel unhappy about this. Pornography is destructive. It undermines and destroys relationships and leaves young people who are exposed to it with distorted views about what loving relationships are about.
It so often puts women and girls under pressure to do things that they do not want to do and left feeling inadequate. This arises because the men/boys see things on their porn channels and then feel deprived if their partners are not doing the same things for them. Hence the undermining of relationships. They find themselves unable to distinguish between things that actors do because they are being paid for it (or worse still not being paid, but being provided with drugs to feed a habit that keeps them locked in), and loving relationships based on mutual respect.
I can attest to these things from my professional life, which involved counselling. Porn is destructive, as you have found out.
The important thing is that you do not feel bad, or some sort of prude, because you are unhappy about this. You have a right to your feelings and to express them.
You need to tell your OH what your views on it are and proceed according to his response. If between you you are able to come up with a way forward that is acceptable to both, then that is fine; if you find that this is not possible then it is an entirely valid reason for ending a relationship - although I recognise how hard this must be after so many years.
What you must beware of - and what so often happens - is allowing him to make you feel that it is you who have a problem - that you are a narrow-minded prude. Do not buy that one! You have a right to your own feelings.
I am sorry that you are having to deal with this.