The true feeling of considering sex as the ultimate expression of love makes you stuck up with one aspect of intimacy but strictly speaking, sometimes you don't have to carry any emotion of love and can still gain orgasms through intense sex. Even though you sleep with someone you love, the most, don't expect that every time you have sex with your partner is all and only about love. Sometimes it could be beyond love and sometimes it could be plain lust.
Now you may wonder, how your partner can have sex with you without carrying the emotion of love. Of course, your partner loves you, and it has nothing to do with various kinds of sex you both have all the time during your relationship. Some partners who are particular about a few sexual behavioral patterns, make it a big issue when they miss that romantic aspect in love. Practically, regardless of sexual orientations and gender identities, no partner can have sex only when he/she/they want to express the emotion of love. Hence, there are a few more kinds of sex, a person may encounter with one's partner.
Casual sex comes in the form of having sex in the middle of the night when you both get aroused out of nowhere, having sex in the shower when you feel like dragging your partner inside your washroom as your silly relationship tactic, having sex when you feel bored in the Sunday afternoon, having sex when you have nothing to do but screw each other so that you can kill some time by spending time together. These forms of sex don't need to be planned particularly and don't require expressing emotions when you are inside of each other. Aren't they too casual to even consider as the ultimate expression of love?
Stress-relieving sex is all about the physical and psychological pressures a person may handle in one's work environment. Under such circumstances, your partner needs you and your body to act as the sensual channel of taking the stress out of one's system. There's no need of expressing love over here. You need to understand the biology here instead of adding stress on your partner by inquiring about the aspect of love when your partner misses out on saying "I love you" in the middle of sex. So, next time if your partner comes from the office and signals you to have sex, understand the need for the human stress-relieving aspect and get along with it. You don't have to objectify yourself. Feel good that your partner chooses you to relieve his stress instead of cheating on you. Don't you think, that's love and being true to you?