I found out my boyfriend is HIV positive and that he has already infected other people.?

I am having a real hard time defining people in this world. I always had a very protected life, my family has always been wealthy and protected me from many evils of the world. But ever since I went out to college my perspectives of the world have been falling apart. I just found out that my boyfriend is HIV positive. And that even knowing that he had unprotected sex with a young guy not caring that he could have destroyed his life. To me he has always been very good and noble. Always protected me, always took care of me and I love him so much for what he used to be to me. But now I am struggling to these new realities that have been presented in my life. Is the world really like this? Do people really screw each other just to feel not caring that they might be destroying an entire life just for a few minutes pleasure? Even when those people can be good, great people in the eyes of so many others? Is the world this dark? Even after all we have and know we could have? Are we still this primitive? That we cannot reason logic with desire? Why? Suddenly I see all my hopes and illusions about life, people, society, humanity falling apart. I am so scared of the world we live in now. Can no one be trusted? Even the ones we love? Is this what humanity and people are? Why? Why? How can we know who to trust? Who to love? Who to hate?