First of all, chinese is different from english in terms of grammar logic, you can not just find direct translation that connects a sentence pattern in english and a corresponding sentence pattern in chinese.
However, i think you are looking for "我原本以为。。。,但是现在我发现(事实)是这样的。。。" to "i thought" and "在这(现在的情况)之前我一直以为。。。" to "i had thougt"
Again, above are just one of many ways to express the same thing, there is no fixed sentence pattern, what you have to understand is to use the correct adverbs and verbs to let people know what the real meanning behind your words, but not a correct pattern.