while+过去进行时,是不是总是sb.+was+doing sth

不一定.
while+过去进行时,sb.+was+doing sth
主语是我是I was,但当主语是我们,他们,你,你们 we,they,you ,you时
be动词用were
I was doing the same thing as he did.
但在虚拟语气中,从句中的be动词都用were
For example:If I were a bird,I will fly to the sky.