Will I get fire from work? (Safeway)?

I have a position as a courtesy clerk... At first I did not know what it was, until I start working. I must say this is a pain in the butt job. I couldn't go for another positions aren't any. So anyways, as a courtesy I have to do a lot of work like bringing carts, sacking, running around the store and check for the price. Omg I've been working there for two weeks and I just want to quit. But if I quit how am I going to find another job. Back to the topic, I think the manager of the store doesn't like because I'm not like who I am when he first met me. I was very bubbly, friendly, and ready to work. But working as a courtesy clerk my smile slowly fade away. I couldn't say it to anyone but complain to some of the co- worker that my job sucks! My supervisor cut down my hours on Saturday and called the expert courtesy clerk in. I felt kind of sad and my intuition telling me that I'm going to get fire. Plus, my work days aren't enough. I only get two days out of a week. And one last thing how can they fire you from a grocery store? (Safeway)