If you're translating the sentece literally, use Being totally awesome since a long time ago.
Now, if you're writing something new, you have loads of options, considering you have some leeway and don't need to translate Desde muito tempo literally. Some of these options are:
Being totally awesome since long.
Being totally awesome since long ago.
Being totally awesome since a long time.
Being totally awesome since a long time ago.
But the phrase seems to be what a teenage would say. It looks exaggerated.
I'd suggest, if that is not the intent of the sentence, you to change the first part of the phrase.
I would avoid the word totally and try using incredibly, utterly, absolutely etc. Instead. I could even completely avoid these adverbs, as awesome (meaning impressionante, incrível) is already an adjective "powerful" enough to stand alone (without adverbs accompanying it) in the fist half of the phrase. I could also change awesome to awe-inspiring, amazing or simply incredible, depending on the context of the scenario.
I hope I helped.