It depends on what you mean by partner. If this person has not married you, then they're not entitled to sex with you, period. Now within the confines of marriage, it's not okay to withhold sex because that implies emotional abuse. However, it is perfectly okay to refrain from laying there until they're done because it simply will not be the spiritual, holy, transcendent, uniquely human sexual experience that you're aiming for. It sounds like low grade trauma to me. No, you are not obligated to be taken sexually advantage of by your spouse.