Today was the second time where I left work because I wasn't feeling good. Today, my stomach was aching so bad, but it was payday so I went back into work to pick up my paycheck a few hours later. The manager looked P.O.'d and said "I thought you weren't going to come in because you were SO sick this morning." Now I'm scared she might fire me. I've only been working two weeks and missed two days already because I felt sick in the morning. I told her already that I tend to feel sick in the morning which is why I changed my availability so that I won't be up so early. My grandparents said not to say anything or apologize to the manager unless she brings it up. I've been worrying about it all day that she might fire me or not believe me when I feel sick.

What should I do?