I assume given the subforum this is in, you are in the T-45? Don't worry dude, flying form in that thing sucks balls. You're trimming like every second, every power correction, it just is a real plane. The F/A-18 isn't like that. At least I don't think it is. I don't think I suddenly got so much better at form between T-45's and Hornets at least. You just need some reps and sets, you'll be fine. Most people aren't naturals at this stuff. At the real nuts and bolts level, it sounds like you might be a little "binary" on the controls. Don't make a big control input and wait for the response. Make a small one (I realize you don't know what "big" is, so just a little less than normal, obviously not so little you hit your lead), and see if it is enough, before adding more if it isn't. You're getting yourself into a PIO it sounds like, if you're trimmed out to start with (a couple seconds is all the T-45 is good for trim wise in close formation anyway)
That being said, it sounds like you might be getting in your own head about this. That is the #2 killer of students, after #1 just not being prepared/bad attitude + sucking. So go easier on yourself. That isn't to say don't take it seriously and not try to improve from all your mistakes. Just know that we all make them, especially when you are learning, and letting one mistake cascade into a series of mistakes because you are mentally stuck on 5/10/30 minutes ago in the flight, is not what you want. Make the mistake(s), brush it off, and keep doing your best. Way easier said than done, but that is how you crack that nut. Nobody expects you not to make mistakes. As an instructor, I get to do my job when you do, and teach, which I like. None of us get mad when there is a teachable moment.