Cultivating Implicit Trust?

I just want to know, does anyone else out there have difficulty with implicitly trusting someone, in particular, the person that is supposed to be the closest to you. Like a best friend, or a boyfriend/girlfriend, sibling, etc. I have always had issues with this. In all of my relationships I have never 100% trusted anyone and divulged ALL my secrets because there is this hidden part of me that just has these reservations about all people. I have been hurt and manipulated by so called "friends" and evern family in the past and I am partially afraid of being judged or people's perception of me changing if i am that honest. I am also afraid that I have this need to have the upper hand in my relationships, primarily my friendships ;( I am always the consoler and advice giver, while my friends are always the ones spilling out their hearts. As much as i wish I could do this, I feel like letting go will give them my power.. will somehow make them have something that they could use against me.. something that makes me appear weak. I want to know how I can get over this because there is something that i really feel i need to share with my best friend, but i am not sure that how i feel is subject to change, etc. It has to do with someone very close to her so I dont want to ruin our friendship or make things awkward. how can i learn to implicitly trust her and just tell her, regardless of whether or not what i am feeling is lasting or fleeting. how can i get past my idea that she will judge me, she has been so loyal in the past with very few slip ups that she didnt feel horrible for but still... its so hard for me and i need to talk to her. :(