How do you say

I wore this shirt for just a month and it’s gotten smaller.

..in Chinese?

这件衬衫我刚穿了一个月就小了。

zhè jiàn chèn shān wǒ gāng chuān le yí gè yuè jiù xiǎo le 。

How do you say "We plan to start working out together next month." in Chinese?