Work is making me very anxious and stressed

[miniholly]

Hi,
So I've worked at my new job now for the past 2 weeks or so now. I've only had a couple of proper shifts as the first 2 days in work were just training.
I'm contracted to work 8 hours a week and last week I worked 16 as my boss text me and asked me to work the Saturday as they were short staffed so I did it even though I was very unwell and had worked the late shift the night before, however in the past couple of days alone I have received 3 texts off her asking me to work extra hours.
I was working 12 - 4 yesterday but she text me asking me to work til 8. I had no safe way of getting home at that time so I politely said no even though she asked me the same thing on Monday and I told her the exact same thing.
I have today and the weekend off and this morning she text me again asking to work 11 - 3, I was asleep when I received the message and it was 11 when I woke up as I still do not feel well so I didn't reply obviously.
I'm scared shes going to ask me to work the weekend which I can't do as I have projects for college to do, its really starting to stress me out as I'm scared she'll give me the sack if I don't work extra hours like she wants me to, I also can't enjoy my days off as I'm scared she'll text me asking me to work.
I will work additional hours when I can do but its starting to destroy my plans already, last week I was supposed to take my Auntie to the train station with my mum as she lives in Scotland but I couldn't as my boss asked me to work additional hours.
Please help someone :( I'm so anxious and stressed about this, its only been 2 weeks but already I'm starting to think of applying for more jobs as its all too overwhelming and not to mention intimidating for my first part time job. I've already worked my 8 hours this week too.
I'm only in college 2 days a week but I'm always in until 5pm and always have a lot of projects to do.
I really don't know what to do at all other than talk to her but I don't want to sound lazy, its just I simply can't work extra hours some days.
Please help :(

[BobbyDog]

It is difficult, but I think you have to be firm with your boss. Tell her you were only contracted to do 8 hours a week and you are unable to do more than that because of other commitments you have. You don't need to explain anymore than that to her. She is taking liberties.

Your mental health and college work are much more important than your part time job.
Look for something else less demanding until you have more free time.

[Stormsky]

Agree, tell her the reason you wanted a contract of 8 hrs a wk is because of college...and you don't have the time to regularly be doing extra hrs at short notice.... Tell her with some notice you may possibly be able to do extra on occasion.

[Daniel Copp]

I agree with the above posts, be firm and know you are doing the right thing.

[miniholly]

Thanks for the replies, Im actually so scared she'll text me again tomorrow I dont understand, if they are so short staffed they should hire more people, Im hoping that when the Xmas temps start this will stop, atleast for a little while. After Xmas Im going to hand in my CV at some makeup counters as that is truly what I want to be doing and makeup is what Im studying at college atm I feel I have so much more to give than sorting out clothes and to be made felt guilty for not working extra shifts 24/7. I know I should be grateful to have a job at such a well known store but I cant if Im feeling so stressed