Can I use 余怡蜜 as my Chinese name?

Yes, you can. Yu Yimi, or 余怡蜜 in Chinese, is a great Chinese name choice for you. The surname 余 could mean extra and surplus. And there are lots of people sharing this commonly seen Chinese surname, for instance, Yu Nan, or 余男 in Chinese, an actress from mainland China and Yu Yue, or 余玥 in Chinese, an actress from mainland China.

Here is a picture of Yu Nan.

Here is a picture of Yu Yue.

The Chinese character 怡 could mean cheerful and happy. And you could find that it could be used as a generational name, such as, Liu Yijun, or 刘怡君 in Chinese, an actress from mainland China and Jin Yilian, or 金怡濂 in Chinese, a scientist from mainland China.

Here is a picture of Liu Yijun.

Here is a picture of Jin Yilian.

The Chines character 蜜 could mean honey. And it could be used as a female given name, for example, Li Mi, or 李蜜 in Chinese, a former TV program host, and Zhao Mi, or 赵蜜 in Chinese, a lecture at Minzu University of China, or 中央民族大学 in Chinese.

Here is a picture of Li Mi.

Here is a picture of Zhao Mi.

So, you see, 余怡蜜 is a great Chinese name for you.