Is being a pronoun

No, the Word 'being' is the present participle, present tense of the verb to be. The present participle of the verb is also a gerund (a verbal noun).

Examples:

You are being very difficult. (verb)

A strange being appeared out of the darkness. (noun)

A pronoun is a Word that takes the place of a noun in a sentence.

Example: Jack usually takes the bus to work but today he walked. (the pronoun 'he' takes the place of the noun 'Jack')