As long as you're doing the best you can, it's fine. Thirty days isn't long enough to be comfortable with loading. When I was new the place blew my mind with all the activity, shouting, pkgs tumbling everywhere. So many new things to learn and no one seems to have time to help. I was on the preload with three pkg cars and it took me months to really feel confident.
As you get more familiar with the load you'll find that, by scanning with your eyes, you can pick out two pkgs going to or near the same place in your trailer. If they're not too large grab them both. You'll learn shortcuts but only after you've had time to learn the job. Take it easy on yourself. Also, watch those loaders who seem to have extra time. See what they are doing right and don't be afraid to ask them questions. They were also new at one time.
You don't have to be the fastest or best. Work safe and follow the methods they teach you. If your sup says you're too slow just ask if they have any suggestions. I've done that and learned some pretty good tricks. Some are just blowing wind from their butts and you'll soon recognize that. If they bring someone to help, smile and say thanks. Don't feel it's because you're not fast enough, it's because there's too much flow at the time.
So hang in and hang on for the ride! Be safe and be satisfied with yourself.