ANXIOUS and NERVOUS for job at subway!?

I've been working at Subway for a couple of days now and it is not going good at all! I keep forgetting the sub formulas while making them! I know them when I'm not making the subs, but always forget when I'm actually making them. It takes me forever for me to ring up their order on the till. My manager has yelled at me so many times and it gets really frustrating. I can't just quit because I need the money for university in the fall. Also the thing is I CAN'T stop thinking about my job when I'm off work. I'm always so nervous and I wish I didn't have to work. I need to know how long this discomfort and anxiety will last and how long it will take for me to get used to the job (making subs, doing the cash register, prepping the meats/vegetables, and even closing the store!) Also how can I stop the anxiety when I'm off work!