It seems to me that this is not about the words, per se, but the meaning of the words. There are solid, important, internal reasons why this sticks in your throat, why you can't say these phrases, even though you know them to be true. This is important information for you – a goldmine in fact – that could reveal a lot of internal issues that drive you, even in other aspects of your life. Whatever feelings of disloyalty, shame, denial, anger, betrayal, anguish etc etc that are stopping you from speaking are worth confronting and owning, or I suspect you'll only be partially liberated from your painful background. (And you may be avoiding getting into how very painful it was – denial has probably served you well up to a point. But it may be time to jump this hurdle, and this may be the timing of your question.)
Of course, being able to write these things is important and useful. But speaking has its own unique dynamic having more to do with publicly acknowledging and claiming what happened, overriding shame and embarrassment. I suppose you could probably push through your resistance and make yourself say these things, over and over again, with greater and greater ease. But you would probably get further by exploring the meaning of all this on deeper levels. Some good old fashioned, traditional psycnodynamic examination of this in counseling with a knowledgeable therapist could yield enormous benefit. I'd go for it. It wouldn’t be easy but it would be worth it.
All best wishes to you,