I do not agree with all the above posters - life is too crazy to be miserable. That said, there's a difference as a new nurse between feeling "lost" and then hating your job.
Also, it sounds like you just don't like the hospital - but you like the critical care role? This does bring up a few issues. It's hard to get critical care experience as a new grad nowdays, and it'd be hard for you to transfer doing the same thing without at least 1-2 years. I think that's where these posters are saying "stay where you are", and I slightly agree.
The most ideal thing to do would be to job search
while you retain your current position; and not leave until you have another one. I would have to agree it'd be almost ignorant to leave your position without another one.
If you're trying to switch specialties, start searching in February (or whenever it is you'll have six months, I think I remember reading August start date). I would try to stick it out for at least six months experience.
Good luck, and know that you're not the only one.