Trust... and all it's difficulties.

I have a blatant problem with trusting people. I can't think of a single person that I trust unfailingly. There are way too many doubts and worries in my mind that keep me from being content for longer than five minutes at a time. There is something wrong with me, I honestly cannot accept any explanation that isn't the worst case scenario. I am given a perfectly good explanation that must be true (as it has been promised to me), but I go ahead and believe just what would make me want to cry my heart out. What do I have to do to be able to believe things people tell me? What is it like to trust so easily? I want to be able to hear an explanation for something bad and believe it. I want to trust in all the good things instead of the bad. I want to know that I'm not being lied to by the people I love most... I have the answers, I have the explanations, why can't I be satisfied? I'm trying, I really am. I'm reminding myself over and over that the people I love would never lie to me. But, it's so hard to believe that I can be happy... Help me.