I personally believe in giving any job 1 year. 1 year is usually the amount of time to become proficient in a new job in my book. It usually takes less time than that but for me a 1 year is an easy bench mark and is a realistic goal. I loved the ER after a few months whereas I hated working as a private ambulance after 8 months (left because I started nursing school
so I couldn't give it a year). If it is giving you a lot of stress and you do not think you can work it out, I would begin applying to new jobs.
However, they may not consider you until you have more experience under your belt out of fear you may jump ship. I would use excuses like you want to work closer to home, a unit where you can connect better, it's your dream job, etc when you are asked why you are leaving your previous job.
I always feel like I am horrible at my job whenever I start a new one. I switched from an ER background as a paramedic to an ICU and I feel like I am not as good as my job due to a different flow of how things work. After a year if I do not like it, I will consider moving to a different unit.