Commonly, we would equivalently say "This is all my own work".

That's not to say that your expression is incorrect, but it isn't as easily understood by native speakers of English as the equivalent expression provided above.

#TL;DR

It doesn't make much sense to use your particular expression.

Commonly, we would equivalently say "This is all my own work", for singular, or, "These are all my own work", for plural.

Yes, you can use "achievements" instead of "work", but then drop the "all" and the "own" from the above sentences.

That's not to say that your expression is incorrect, but it isn't as easily understood by native speakers of English as the equivalent expression provided above.

#TL;DR

It doesn't make much sense to use your particular expression.