You can have sex (i.e. a sexual act or encounter), or even a sexual relationship, without having an intimate relationship. There is nothing psychologically wrong with having a – let’s call it – sexual-only relationship, it is just that it is not in itself an intimate relationship. Sex can be combined with closeness and intimacy, but this does not happen automatically. You can be or become intimate without having sex. And having sex does not automatically produce closeness or intimacy.
Similarly (but not further pursued here), there is nothing wrong about an internet-based relationship with another person, but it will not automatically lead to or turn into the equivalent of an intimate relationship (though perhaps it might).
A sexual relationship can grow into and become (part of) an intimate relationship, but this does not necessarily happen, and there is nothing easy or self-evident about the transition.
Sexuality and intimacy
The idea of an intimate relationship is considerably broader and wider than a sexual-only relationship. An intimate relationship can include sex, once-off, ongoingly, at intervals, or not at all. To put it plainly,
I am of the view that you can have sex without intimacy, and intimacy without sex.
Intimacy is more vitally important for people than sex
My second big belief is that intimacy is psychologically more essential for most people than sex. People in intimate relationships can have lengthy periods with sex or without sex, and there can be periods of ongoing wishes for or fantasies of sex without (physical) sex taking place.
Monogamy and non-monogamy
The idea of “monogamy” is that you can (or should?) have only one intimate relationship involving actual sex at any one time. Monogamy is a preference, a belief, and a value. It is not a law or a rule. Being in one or more non-monogamous relationships can and does work. If non-monogamy is combined with full honesty / openness / disclosure about the intimate relationships, many people these days call it “polyamory”.
All possible combinations between monogamy, polyamory, partly not-disclosed non-monogamy, heterosexuality, homosexuality, bisexuality and other queer styles are possible, are being lived, can work, and there is no psychological reason to have any issues with them.
However, all possible relationships can, and mostly do, have times that there are problems with them, that they are under threat, that they undermine your well-being and even sense of self. But that is the consequence of human diversity, personal growth and development, and the difficulty of having relationships at all.
Intimate relationships are worth it!