The choice isn't simply 'stay or go'. Talk to the rest of the team. Tell them what you're feeling (that you're not happy, _not_ that you're considering leaving). There's a good chance that there's work to be done that you could focus on that you will find challenging, or that there's something you can do to mitigate the hours you're putting in, or simply that talking it through might reignite the passion you (presumably) had at the beginning.

Plus, don't fall into the trap of thinking the grass will be greener somewhere else. This is your first job since graduating. You don't have much experience yet. Take it from me, almost every job is the same. It's actually easier to tailor your existing job to be something you like than it is finding a job that will suit you better. (Caveat: This is true of everything bar the number of hours you're working.)