Would this sound natural, like a fluent speaker?

[Addem]

I want to say "I felt the same even before your message," which I'm translating as "Sentaba el mismo aún después de la post." Did I get it right?

[AngelicaDeAlquezar]

I'm sorry, but not at all.

"Sentaba" is the verb "sentar", not "sentir", which is the one you need. Also, the proper conjugation is not the imperfect, but the preterite.

"El" is a determined article, but you need a neuter article to accompany "mismo".

"Después" is the opposite word to "before".

"Post" is not necessarily the best word for "message", but if you want to use it, it's masculine, not feminine.