I agree with Haddock, if she is truly not trust worthy then maybe you should think about not being with her.. But is it possible that you are doubting her for no reason at all? If she is truly honest with you and is totally  committed to you then would you want your doubtful nature to come between the relationship? I think you should look for proof for your doubts... And if you dont find any, then maybe its time to change your thoughts.. and if you cant, you should not continue with the relationship. You will never be able to be happy if you are always doubting on someone!