Three years ago, I came to the belief that utilitarianism is true. As a result, I pretty much immediately decided that I was going to donate my kidney and a part of my liver.  I decided to wait a year, at which point, I signed up to donate part of my liver (because I expected this have higher expected value.) I was about to go to the hospital for a full day of testing and talking with doctors when one of my parents started to freak out that I was actually going to do it. My parent told me to wait a year so I did. I currently am struggling with a chronic disease so I am unable to donate any organs at this time, but I still feel like, when my disease goes away (which it almost certainly will), I will have a moral obligation to do so. According to utilitarianism, failing to prevent a harm is basically just as bad as doing a harm. As such, it feels like, if I don't donate my organs, I'm basically actively choosing to let someone die.

At the same time, since becoming convinced of utilitarianism, I've also become convinced of strong longtermism, namely the idea that that far future has extraordinary potential value and that this value is so high that it completely overwhelms all of our other moral obligations. If you, for instance, donate to a global health charity to save a human life, you're basically wasting resources that could have gone towards saving 10^20 human lives in the far future by reducing humanity's existential risk.

So, now, I'm at a contradiction. I believe that failing to donate my organs would constitute a serious moral wrongdoing. At the same time, donating your kidney has about a 1 in 10,000 chance of death. Similarly, donating part of your liver has about a 1 in 2,000 chance of death. If I donate my organs and die, I will be unable to shape the long-term future and vastly more harm will be created to the universe than if I had never donated my organs in the first place.

At a very basic level, I think that donating my organs is a very good thing to do and I legitimately would like to do so out of a concern for others, but I believe that organ donation is bad because it could result in excessive harm to the far future. 

I can try to think of ways out of this. Maybe, if I donated my kidney, I wouldn't face that high of a chance of death and I could prove to myself that I'm an altruistic person, which would serve me well in life. If I donated my kidney, it would demonstrate a verifiable commitment to altruism that virtually no one can claim. If I donated my kidney, I would not have the moral weight of letting someone die be on my conscience.

At the same time, if I actually die, it could produce extraordinary harm to the universe.

I'm wondering if others have had similar thoughts and how they deal with them?