On the question of monogamous homosexual relationships, this is my opinion, based on my understanding about what the Bible teaches: promiscuity is always wrong, but lack of promiscuity does not make sex right. An unmarried man and woman can have sex only with each other, but if they're not married they are committing fornication. A single man may have sex only with the same prostitute, or only with his sister, but it is still wrong for him to have sex with her even if he has been monogamous in never having sex with another. A homosexual couple can have sex only with each other, but they are still committing an act which God condemns.
Now, even when and where society legalizes homosexual marriage, this does not mean God recognizes it as a marriage. If society legalized marriage between an adult male and a six year old girl, God is not bound to recognize it as marriage and withdraw his judgment that this is perverse. If society legalized marriage between a man and his sister, this would not thereby change God's revealed will on the sin of incest.
While this may appear to be unfair to the homosexual, it is parallel to what single heterosexuals must also hold to—no sex outside marriage. And, of course, while they have the theoretical option of marriage, many single heterosexuals in actuality will never have marriage partners and therefore will have no legitimate physical expression of their sexual desires. It is true that we each of us has many desires that we are forbidden to act out. The apparent unfairness issue, however, is not exclusive to this arena. The fact that you may have food on the table and someone else doesn't may be unfair. The fact that I have two legs that let me ride my bike 18 miles this morning is unfair when I have a neighbor in a wheelchair. The fact that your pancreas may work fine and mine is a disaster (requiring me to take multiple insulin shots and blood tests every day) may be unfair. Life in this fallen and twisted world is full of unfairness, but God calls us to love him and obey him and trust Him that the guardrails he sets on our behavior are both for his glory and for our good (and that one day, in heaven, he will liberate his children from all the results of the fall).
My feeling on this, is that I do not make up the moral rules of the universe, nor does God seek my permission or approval of his rules. If I did not believe the Bible, I would definitely support the legitimacy of homosexual relationships, just as I would support abortion rights. I'm not homophobic. In fact I was once at a meeting of 25 men where I was the only guy in the room that had not been involved in a homosexual lifestyle--I was neither fearful nor uncomfortable. The thing is, I really do believe the Bible, and therefore I can't hold to these positions no matter how convincingly people may make a case for them. I can honestly say that my desire is for you to experience God's very best for your life—which the Bible makes clear involves your purity and obedience to Him.
Could I ask you to do something? There is an organization called Portland Fellowship that specializes in dealing with these issues. They can be contacted at firstname.lastname@example.org or 503.235.6364, and will gladly respond to this and other questions you might have of a biblical or personal nature. I know them to be trustworthy and I really believe you would benefit from contacting them. They said they would be glad to interact with you, provided you make the first move by contacting them. Just asking them the same question you asked me might be the place to start.
I do wish you the very best. I pray that God will work in your life to accomplish his purpose and bring you true freedom and fulfillment.
For more information, see also this Love Letter to a Lesbian on the Desiring God blog.