Would you say Matt. 5:28 still applies if the woman in question is your own wife?
No... with one exception.
God ordained the marriage relationship
partly to provide a context for the expression of sexual desire (which, of course, He also designed). Desiring one's own wife and thinking about sex with her is a normal, natural, and healthy part of the overall relationship. Normally that should lead to his giving himself to her, and not manipulating, demanding, or self-gratifying.
The exception: where a marriage is strained because of a husband's sinful behaviour, and the wife has withdrawn sexual intimacy
as part of a broader set of boundaries*, I would suggest that the husband is then acting selfishly by imagining sex with her. However, God is the judge; I'm not. I would simply encourage the husband to put that energy into dealing with his own issues so that the relationship is restored all the sooner.
*This is important: withdrawal of intimacy
by itself is a punishment, not a healthy boundary consequence.