What would you do?

I started a job a month ago and it started off great, great pay, great hours, good people, put everything went down hill last week. So I have been working my butt off it is a restaurant atmosphere I’m a prep and I’ve been working my butt off and I write down everything I do when I get home so I know what I’ve done for the day, I’ve had my coworkers come to me and say how are you so fast, anyways I look at the schedule last week and I’m only scheduled one day next week, I’m just like wth, I go to work and ask other coworkers and they said their days were cut to but not by that much, and when I went to ask the manager after my shift, he says I’m the one of the bottom two, y’all I’m offended, I know I’m not and when naming off all the stuff I’ve done for the day he looked confused like did I really do all that, then asked when the next day I’m supposed to work so he can stand in back to watch me, so they are just assuming I’m one of the slowest and haven’t been watching me I lost all my working days, I’ve been crying all night, and now afraid I’m gonna lose my job, how am I supposed to prove them wrong when I’m only scheduled one working day a week, it’s not even right, you would think they would want you to improve if that was the case.

Also we all started on the same day the restaurant just opened. Sorry for not clarifying, I’ve never called in, always on time, and already there has been some all ins, coworkers that have been late.