Stressed during teaching practicum. Is this normal?

I recently started my first teaching practicum for literacy and social studies. I overall love my mentor and enjoy the students. The practicum takes place Mondays and Wednesdays from 8am-4pm every week. My mentor teacher asked me to come in at 7:30 since classes start at 7:55. My friends in the practicum are doing way less work. I am about to start week 4 and some of them are still observing like they're supposed to. My mentor was having me do a math lesson on the first day and it's not part of my practicum. I am also grading papers and staying late to sharpen pencils and help clean. I have done math lessons for weeks now as well as literacy. She knows i'm social studies/literacy. She also knows I am not supposed to be doing lessons until half way through the semester. I feel burnt out already and I am taking 20 credits at the college which I can't drop. Idk what to do and all my friends just help out in small ways and I feel like I have taken over the class. I even went and bought supplies for her lessons for me to teach. I am so stressed and I have to do this next semester with a different mentor for science and math. I had to quit my job to do the practicums and I am working more than I was before but for free. I kind of just want to drop out and forget it and go back to working as a waitress. Hello again. Thank you to those who have given advice. I wanted to clarify that my practicum is 16 weeks. My program set it up where the first 8 weeks are supposed to be full-time observation and the next 8 is observation and teaching. I am only required to do 4 lesson plans.2 for social studies and 2 for literacy. I was a transfer student so my adviser passed me for the 20 credits to graduate only 1 year late instead of 2 years late since some classes are only offered during certain semesters.