あなたの気持ちが分からないって英語でなんて言うの？

The two sentences you see provided above are terrific ways to express to your listener that you do not know how they feel towards you. In the first sentence you will see the word clear and in the second sentence you will see the word get. Both of these mean to understand. These words are apporpirate for informal settings, like talking with close friends or family members.

If you are unsure of something then you can also say you don't 'understand'
feelings are the way we think about something so like, love, hate etc

Strictly a spoken way and not to be used in written English. This phrase is used between friends.
When someone uses the phrase "I don't get..." it means that they are not understanding something. The rest of the sentence explains what someone is confused or unsure about.

This is the English that is MOST commonly used within Britain and sometimes within the USA as well.

This is a simple phrase that can be common. The best way to say this phrase would be to use the examples and substitute words for good measure.