Describe Wwhat Yyou Aare Wwearing Rright Nnow?.

It sounds more like an instruction or a prompt, rather than a direct question. Only the word "Describe" should be capitalized.

I a’m wearing pajamas whichthat I'’ve wornhad for years now.

n defining relative clauses, "that" is more appropriate than "which". "I’ve had for years" is a more natural way of saying that you’ve owned something for a long time.

My family saidys I should buy new ones, but these are my favorites.

Since this is something your family regularly says, it's better to use the present tense "says" instead of the past tense "said".

I'm a I’m the type of person who likes to keep things.

Since the subject is "person" (singular), we need to use "likes" instead of "like". And this phrasing is more natural and sounds less awkward than just saying "I’m a person."

Describe Wwhat Yyou Aare Wwearing Rright Nnow?

You don’t need to capitalize every letter of each new word :)

I am wearing payjamas, which I've worn for years now.

’ pyjamas’ is how it’s spelt in the UK, it depends on if you’re learning US English or British English.
Pajamas = US
Pyjamas = UK

My family said I should buy new ones, but these are my favourites.¶

Favourite = British English
Favorite = US English

I'm a person who likes to keep things.

I am wearing pajamas which I've wornowned for years now.

Nitpicky, your version is also good but I'd word it like this.

I'm a person who likes to keep things.

Describe What You Are Wearing Right Now?

My family said I should buy new ones, but these are my favorites.

I'm a person who likes to keep things.