It's supposed to be a genuine question a character asks himself after waking from a dream. I've tried different online translators but I'm not sure if I can trust them. Any help would be nice.
While @FlatAssembler is correct that that's one way someone could say "Am I really alive?" it might not necessarily be the most idiomatic way.
If what you're looking for is an expression of surprise—like, "Holy moley, I can't believe I'm alive!"—then what you want is an accusative of exclamation: Mene vivam? if your character is female and Mene vivum? if your character isn't. That means essentially "Me, living?" and there's an implied esse ("be"). You could also do *Mene vivere?" which is "Me, live?" The "really" is left out of the literal translation, but it's communicated by the word endings, which in this case can imply a sense of amazement.
If what you want is a genuine inquiry by somebody trying to find out if they're alive rather than dead, you'd probably use the fairly general verb vivere: Verene vivo?
If what you want is a genuine inquiry by somebody or something trying to find out if she/it is animate rather than inanimate, you'd say Verene sum animans? which means, pretty literally, "Am I animate?" but which in Latin doesn't have the same kind of technical connotation.