I have been busy since yesterday.
我从昨天就很忙
为什么不写成 I have been busied since yesterday.
这里句子的成分你搞错了
这里不是主谓宾，而是主系表
原来是 i am busy
这里是将am变成完成时，就成为了I have been busy
am就是动词，系动词