如果你没有完成作业，并且需要写一篇关于这个主题的英语作文，你可以参考以下几种表达方式：

我完全忘了写作业

I totally forgot to write my homework assignment.

我有太多其他的事情在脑海里，完全忘了它

I had so many other things on my mind that I completely forgot about it.

我至今还没有写完家庭作业

I have not finished my homework yet.

这些表达方式可以帮助你描述忘记写作业的情况。如果你需要更详细地描述你的感受或者解释为什么忘了写作业，可以进一步扩展这些句子，例如：

I was so caught up with other activities that I neglected to do my homework.

I feel terrible for not completing my assignment. I should have been more organized.

希望这些建议对你有所帮助!