You're right that sex isn't necessary for happiness, I meant to preface that part with "for most people" or something along those lines. That was my bad. In fact, I would actually even say I'm in the group of people who don't feel it's necessary for my own personal happiness. But still:

God made a pretty awesome world and wants us to also enjoy sex

Unless you're one of the 10% of people he decided to make gay, apparently.

Again we gotta go back to, why did god even give women an organ that has no function other than pleasure, and why did god give men the ability to have orgasms through anal sex (which literally can't even result in reproduction)?

I guess what I'd really like to know is, what's your basis for believing that god believes gay sex is a sin? Is it because the bible says so? Because the bible says a lot of other crazy things are sins, like wearing clothing made of mixed fabrics, etc. You have to remember the bible was written by humans and humans are stupid. If you want to base your beliefs off what you think god wants, why not look at what he created instead? Because even though I don't believe in god or creationism, it certainly seems to me just from looking at our bodies that we were "designed" with gay sex in mind.