If you are unhappy, I would first consider if is your job that is at fault. Most commenters here have expressed an opinion which I think I would characterise as - don't expect your job to make you happy. This is valid. I know people who have worked in organisations which do highly socially conscious work, but still experience the same disappointment and frustration. So first just check it really is the job.
But I too have found myself in jobs where the job itself was making me seriously unhappy. On reflection it was in every case because I was being badly managed. Having finally worked that out, I successfully got myself moved internally on a few occasions, without ever revealing the real reason (sad, but you are looking to improve your lot, not become a whistleblower). I found that had the advantage of knowing what to expect to an extent not often available in a job interview. YMMV.