how to deal with anxiety at a new job

i literally don’t even have to go in until 5 but my stomach is killing me bc i’m so nervous. it’s just the fact that i’m expected to stay and if i get too anxious and leave it’ll be a whole thing. and it’s embarrassing 😅 i’ve had to do it a few times. i’m looking for help from people who also have stomach problems from anxiety bc that’s my main issue. it’s genuinely flares up my stomach so bad and im not sure how to soothe it. please let me know