Mercutio,
I'm really sad to hear about your current situation, and I think anyone who has ever cared about someone goes through what you are at some point in their life. I know it might be a little presumptuous of me to say this, but the best thing for you now might be to get out a bit more, perhaps go to the nearby big city once in a while just to walk around and see people. Maybe something can be done about your allergies so that leaving the four walls behind is a bit less onerous for you. I know this works for me when I'm down, and the exercise puts me in a better state of mind. I can personally relate to your not feeling comfortable with unscripted social situations, so my idea of just randomly exploring the city is a good way to get out and see people without having anything beyond superficial contact with them.
It might not be exactly what you want to hear now, but it is possible to enjoy life without a "significant other" if it comes down to that. Consider that most marriages are unhappy anyway, and that you eventually end up alone. I think the most important thing you can do is to make peace with yourself, and realize that no matter what you do, at some point life will treat you unfairly. As long as you tried your best, there is no reason to get down on yourself, and from what you describe, it certainly sounds like you poured your soul into your relationship with Amy. Only the future will tell if you're destined to be with her, with someone else, or alone.