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 (http://forums.tomisimo.org/showthread.php?t=9873) 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.