Man's orgasm vs. Female's orgasm
A man's orgasm has a direct effect on producing an ejaculate which is naturally oriented toward fertilization of the woman (essential for procreation). It therefore should always be in the reproductive channel (vagina) for which it is objectively oriented. If it is not, the act is fundamentally frustrated in its objectivity and is therefore contraceptive in nature. That said, even if you fondle your husband or orally stimulate him, he needs to have his orgasm where it is intended. If he accidentally ejaculates before hitting his target, it is not a sin, provided he did not intend that — many factors can affect a man's control and he is dealing with his own humanity and weaknesses. We are simply imperfect, so be patient with him. What he is striving for is keeping the integrity of the act along with enhancing the bonding love of your intimacy.
This is about the intersection of the procreation and unitive dynamics of our sexuality. We were given the gift of sex to be fertile and populate the earth, but also to draw a tight bond between a man and woman who have committed themselves to a faithful covenant of Marriage so even when the procreative part of it is not effective, the unitive dynamic is still there. It binds us together whether we conceive a child or not.
When we divorce these two components from each other something goes wrong (I.e. artificial contraception disfigures the act, procreation without a conjugal act (mere test tubes) disfigures the act). We keep openness to life, so that God is ultimately in charge, and do our best to fulfill the other in a loving way so they have all the benefits of the loving sexual act. Orgasms are a healthful, holy outcome for a sexual practice in marriage. God designed our bodies to work this way. Our society, however, is hell bent on divorcing the two aspects of the conjugal act from each other. Procreation on demand is much more popular, by any and all means possible while being in a loving marital relationship is completely passe or out-of-date.
A woman's orgasm, while not absolutely essential for reproductive fertility (she can conceive without one), does amplify the fertility of the act in a biological way (the spasms of the cervix help move sperm closer to egg), but moreover allows her to feel satisfied and complete.
God intended sex to fulfill both partners, so if the man climaxes during intercourse but the woman has not, he needs to help her get there to complete the act. To neglect her, in a way, is a sin of omission. His responsibility is to serve his wife — even if it requires manual stimulation.
Sex is beautiful as God designed it, life giving, and incredibly bonding and pleasurable — but it can also be a source of great stress when pressures and other worries burden the mind so, in the end, your climax needs to be with your husband, not isolated.
He can be the one to stimulate you there or anywhere you choose, provided it helps you to get there and completes the act. Just don't seek fulfillment and climax without him, or without the context of intercourse being part of the equation.