Bernard Marx, at least at the beginning of the novel, has very different ideas and desires when it comes to dating than everyone else that he meets. He lives in a society where "dating" doesn't even really exist; dating is a ritual that couples go through to see if they want to marry each other. In "Brave New World," marriage does not exist. So, "dating" in their society simply means spending time with another person, and having a lot of intimate relations, but no commitment whatsoever. Commitment is shied away from, and the men and women "connect" (physically, at least) with almost everyone that they come into contact with, that expresses a mutual desire.
Bernard, being an unattractive, surly, and rather anti-social male, doesn't have as many chances to hook up with females as other stronger more classically handsome and social males do. So, he is not as popular. He also wants to spend time talking to the women he meets, being alone with them (which is almost never done on dates until the physical stuff happens), doing non-group activities, and pondering deep things that most of the people in his class don't even think about. He broods and sulks over the fact that no one has the same ideas that he does, when in fact he really just wants to fit in. We see this later on when he becomes--briefly--very popular, and hooks up with as many women as he possibly can, and seems to enjoy every bit of it.
Bernard's unusual cravings for solitude with the women he meets, conversation, and a deeper level of emotional connection, stems mostly from his dismay and disappointment at being ostracized in his society. He wants acceptance from women, but acceptance that says they like him for being different, because he is. He doesn't "fit the mold" of being with tons of different women, partially because they don't want to be with him, and because he doesn't enjoy group activities because of his rejection and being made fun of. His unusual dating tendencies stem from his position of being "different" for so long.
I hope that these thoughts help a bit; good luck!