First I should clarify that this question is (fortunately) entirely hypothetical and academic, so please don't worry about me (I'm fine).
I am trying to figure out a seeming conflict in the broad remit of coercive and controlling behaviour (as defined in the The Serious Crime Act 2015) and the principle of sexual consent. Though the newness of the offence means there aren't many cases on the subject, the guidance from the Cheshire Police, though hardly legally binding, indicates that it would be a crime to withhold affection in an attempt to punish one's partner.
Indeed, it's easy to see how, in colloquial rather than legal terms, deliberately withholding sex could be an attempt to coerce one's partner, and abusive. The linked definition in the Serious Crime Act covers any behaviour designed to have a serious coercive or controlling effect on their partner, which is so extremely broad that deliberately withholding sex as coercive quasi-blackmail clearly seems to qualify.
Yet, accepting that this abusive behaviour constitutes a crime would suggest that people in a relationship are obliged to periodically have sex, even if one of the people wishes not to (albeit for malicious reasons). That would be repugnant, and undo the precedent of R v R  UKHL 12, which clarified (shockingly late) that marital rape is a crime in England and Wales.
Leaving aside the practical objection that the Crown would be unlikely to find a prosecution for just withholding sex as in the public interest, in this conflict of laws, which "wins"? Both outcomes seem unappealing: one lets off emotional abusers and the other forces people to have sex against their will.