3 mos. is nothing. It takes time and experience to find your groove. Healthcare at any level is hard work, and it isn't for everybody, but if you have the desire, you're well on the way. (If you find you don't particularly have the desire, there's no shame in that--like I said, it isn't for sane people--er, I mean, everybody...)
This is a human endeavor, and we who do it are human. I have what I call the Urp Scale. It's like the Richter Scale, but for puking. A 3.0 is barely queasy, but at 4-4.5, you're actually making "Urp" sounds. Around 6ish, you get to taste your own stomach contents, and by 6.5 there may be actual emesis. 8.0 is projectile. So far, I haven't gone past six at work, but that's decidedly unpleasant. But after 8.5 yrs, I rarely go past 3.5.
As far as forgetting stuff, well, I see you're 22, which is a big disadvantage. Still, even young legs have their limits, and in time fatigue will make you more efficient. I'm not a parent, but I know a lot of them, and a lot of the "parenting instinct" you refer to is just laziness.
A lot of people love the ER, but I'm a firm believer in getting floor experience, first. It may be possible, though, to pick up extra shifts in the ER to see if you like it. In the mean time, learn all you can in your current job, but do remember that what you see on the job isn't always the right answer in school. You'll have to decide for yourself which instances are because nursing textbooks aren't realistic and which are because the real world is sloppy--in my experience, both are true, at times. But school will always want the textbook answer, and so will NCLEX. Don't try to do nursing before you're a nurse, but do let nurses know you are in nursing school
. Many nurses just love to teach.
Also, be a team player as much as you possibly can. If you can't deal with code browns, fetch stuff until you can. Do anything you can to be helpful. No matter how good you get at this, you're always going to need help, and if you're quick to give help, you're a lot more likely to get it.
Sorry. Just noticed from your handle and profile that you already are a nurse, and working toward the next degree. That makes some of my advice superfluous, but I hope the general idea still applies.