My first job out of nursing school was pretty close to a stepdown (it wasn't called stepdown, but we were paid ICU rates). It was pediatric pulmonology with trachs and vents, and even continuous albuterol asthma kids. Very sick kids. A lot of watching resp status nervously. On top of that, CF kids with tight IV med schedules and diabetes, random oncology or neuro patients, cardiac, etc. It was ridiculously stressful and that was with a pretty strict 1:3 ratio (even 1:2, in some cases, rarely 1:4 if we had general peds overflow).
To echo ruby, what you are dealing with is most definitely A LOT. Even for an experienced nurse. I'd really encourage you to first, make sure you are prioritizing your sleep and eating habits. This is really, super important, especially working night shift. I'd also encourage you to look for ways to advocate for yourself. This was really hard for me as a new nurse and resulted in a lot of stress that I didn't need to be holding onto. I've recently been listening to a podcast called FreshRN that's focused on new nurses, especially in critical care type settings. They talk a lot about how to speak up for yourself, and that may give you some confidence to do so. Finally, I think it's important to remind you that you are new... you are still learning good time management, meds, procedures, guideline, etc. I don't know about you, but adding my imposter syndrome and self-doubt on top of my stressful unit just about did me in.
I ended up leaving my unit after 2 1/2 years. The first 1 1/2 to 2 were really rocky and a huge strain on my mental health. I loved that unit, but after 6 months of doing okay, I could feel myself starting to struggle again and I didn't want to wait around to see if it got worse. In my subsequent positions (primary care, now school nursing), I have gained so much more confidence in my skills as a nurse though and am actually considering returning to the bedside again in a few years. I'm not perfect and have things to learn in any role, but I'm no longer feeling "out of my league" among the nursing profession, and I now realize I have the capability of learning and advocating for myself to get the help I need to be successful.
Whatever you decide to do though, please hang in there. Either find a way to improve the support you get for yourself or find a job where self-advocacy is easier and grow there. Nursing is a journey with many paths and you are just getting started!