我忍不住微笑.用英语怎么说？

我忍不住微笑.

I could not forbear smiling.

could

aux. “can”的过去式，能够，打算，用于假设语气的条件句，用于虚拟语气的结论句；

例句
The regulations were relaxed and the prisoners could get out and about a bit.
规定有所放宽，犯人可以出去短暂放风。

not

adv. 不，[用以表示否定、否认、拒绝、禁止等]不是，几乎不，未必，没有[用于否定后面的词或短语]；

例句
It became very clear that the incident was not just an aberration, it was not just a single incident.
事实已经很清楚，这件事不是偶发的，它并不是一起孤立的事件。

forbear

vi. <正>（尤指为表示礼貌或耐心而）克制，忍耐，容忍；

例句
I could not forbear smiling.
我忍不住微笑.

smiling

adj. 微笑的，风景明媚的，喜气洋洋的；v. 以微笑表示( smile的现在分词 )；

例句
Behind the smiling eyes lurks the evil that led her to murder the two babies in her care.
她笑里藏刀，杀害了她照顾的两个宝宝。