First of all, you need to take away from your mind the guilt feeling you are having. It is not at all healthy for you: either spiritually or emotionally. By doing this you are owning up to his offence, which you shouldn't. In Islam, each person is responsible for himself or herself; he is a fully mature adult, and he ought to know what he is doing, and that he alone bears responsibility for his actions. Having said this, let me rush to add: I am not in any way implying that you fold your hands and do nothing. Rather what I am saying that you to do everything within your means to save your husband who is drowning. For there is no more vicious a sin than becoming addicted to porn and sexual promiscuity. Such a life-style may lead to eternal perdition. Allah says, "Do not go anywhere near adultery for it is an outrage and an evil path." (Qur'an: 17: 33). After having done your best to help him, if he does not want to help himself, then abandon him to his fate, for no one help a person who doesn't want to help himself. Allah said: You who believe, you are responsible for your own souls; if anyone else goes astray it will not harm you so long as you follow the guidance; you will all return to Allah, and He will make you realize what have done." (Qur'an: 5: 105)
To conclude: my advice to you is: 1) warn your husband of his vices and addictions and the dire consequences of such a life-style; 2) pray to Allah to inspire him to come to his senses and turn to the straight path.
If he is still refusing to take the steps to correct himself; and persists in them then you will have to decide whether you wish to continue to be married with him.
You will find below my previous answer on the Islamic tips to break free of addictions.