You're exactly where I would expect you to be at this point! Give yourself some time. When you do something well--even something you might not think is a big deal--give yourself credit. That will help build confidence.
Also, finding a few unofficial mentors to run thoughts past would help. Most nurses are happy to help a less-experienced nurse.
As far as the recommendation part of SBAR, it doesn't have to be an entire care plan, it can be as easy as recommending a physician assess the patient in person or giving fluid. You'll find that there tend to be typical issues on your ward. I am a NICU nurse and a common order would be a CBC, CRP and CXR. Other units might find that giving fluid is a common response. I guess my point is that with experience you'll get to have a pretty good idea of what needs to be done.
I promise it gets easier! It won't be all that long before you look back and can't imagine ever not knowing what you don't yet know now .