First of all, I am sorry to hear that you and your husband have to bear this burden. I pray that he may be cured of these diseases, in Jesus’ name, that a cure may be found, and that they may not rob you of peace.
Love and intimacy is more than just physical and sexual intimacy. In the marriage vow, you promised to be faithful in good times and in bad, in sickness and in health. When a couple cannot enter into physical intimacy, it is an opportunity for them to explore the other dimensions of their unitive love, to realize that your spouse is not merely a physical body, but a person endowed with an infinite soul, a mystery that reflects the beauty of God.
Love has many languages. Besides physical embrace, there is the language of verbal affirmation, accompaniment, intellectual nourishment, acts of service, symbolic gifts of creativity, etc., all given as an act of self-giving and benediction to affirm and build up the other person. Very often, these various languages of love are more profound than the physical embrace.
As to the struggle with sexual desires, offer the act of abstinence as a gift to the other. Channel that physical needs into the aforementioned alternatives. See your sexual urge rather as one of the expressions of intimacy. When one way is not possible, direct that into the other channels.
Sex is not a necessity in intimacy, even in marriage. It is only a privilege. People regularly have to practise abstinence every day, many for life. The over-sexualize world today has got this wrong. What we need is intimacy and communion; sex is only a privileged expression within marriage when it is possible.
Of course, I understand that it is a suffering. That there can be a great difficulty to abstain, and there can be a great temptation to explore other means of sexual release. I encourage you two to pray for the necessary grace to remain chaste, for the glory of God, but also as an act of love for the other.