It's a long time since I read Brave New World, but weren't the population drugged up to keep them quiescent, and forbidden to form intimate relations, even and especially with their multiple sexual partners?
Yes, SOMA was universally taken and intimate relationships were discouraged. The difference between "forbidden" and what was described in the book was that people were conditioned as children to want some things and to dislike other things, so people conformed with the society's norms because they actually wanted to. There was also social pressure to conform, just as there is now. Another element (it wasn't just about sex) was that people's brain power varied in each class, from Episilons (the most stupid) through the Greek letters to Alphas (the most intelligent). The point was that jobs were allocated based on this and people were in general happy with the work they were given. Today, machines would do the lowest level jobs, but remember when it was written. Essentially, the unhappiness associated with a job that was either too challenging or not challenging enough was eliminated.
The vast majority was perfectly happy with this. A few were not, particularly in the "Alpha" class. Alphas had to retain some individuality as they ran society, which put them in a bind. They were able to want more than the childlike conformity that came easily to other classes (who couldn't help it) but were expected to conform voluntarily for the good of society. Those that just couldn't conform were "banished " to certain islands, where they were allowed to pursue their wishes, which was not really a punishment if you think about it. One of the central characters was unhappy because he was not fully accepted because he was short compared to average Alphas. Once he overcame that by getting some fame, he reveled in his new role, though it didn't work out well in the end. Another was brilliant and well liked but was frustrated in his wish to produce "high art", which was impossible without the emotions (mostly negative ones) that drive it. Both ended up on islands, and were probably happier for it.
The central character grew up in a primitive tribe of American Indians, separated from the main society, and was brought to the main society as an experiment (there's more to it, but I don't want to summarize the whole book). The values of his upbringing clashed with those of society so much that he eventually committed suicide.
Aldous Huxley (the book's author) was anything but a puritan btw, he was something of a pleasure seeker himself; but also a seeker of meaning and purpose. And he certainly wouldn't have conflated pleasure with happiness.
Obviously not as he considered his book to describe a dystopia. I must say I don't know a lot about him. I should do some research.