If you want to stay in the ER, I'd get in touch with your manager or educator via email and tell them you don't feel comfortable in trauma and that you would like a few more shifts of trauma orientation on Weekend Nights. That way there's a written record of you saying you're not comfortable, and they're more likely to address it because reading your email and then continuing to allow you to work trauma without additional training looks negligent on their part. I'm not saying you should try to get anyone in trouble, but if you have managers who are reluctant, I've found that to be a good way to incite action.
Also, it's not clear from your post, but if you're going to tell your co-workers you don't feel comfortable and ask for help, the time to do so, is NOT DURING A TRAUMA. You can tell them/ask them ahead of time so that they can take point and assign different tasks to you, or you can ask questions afterward, but NO ONE is going to explain things to you in the moment. It's critical and they don't have time. They don't mean to be rude, that's just the nature of the beast.
In response to your second question, only you can know for sure, but if you've been there over a year and you're still coming home crying every day, generally miserable, and not 'clicking' with your co-workers, it might be time to think about a position in a different care area, the ER might not be the right place for you. That's fine! No one wants you to be miserable, and there are hundreds of different care areas that you might be better suited to! I'd be willing to bet that if you tell us what things you like/dislike about working so far and what your strengths/weaknesses are, we could even help steer you toward an area that you would be better suited to!