I can't trust my so...

Well I found out I was pregnant yesterday and I told my so to swear he wouldn't tell ANYONE until I was ready and felt more comfortable. He assured me he wouldnt. Well.... what do you know some how today my younger brother knows ... I'm so annoyed I can't believe he betrayed me like that. I don't know what to do now. I'm just so hurt and can't imagine why he would do that knowing I would feel the way I do.