What do you make of this call-in situation at work?

I work as a cashier at Lowe’s. I’ve been there for about five weeks. I’ve gotten plenty of compliments on how quickly I’ve caught on and I’m a good employee there. I show up on time and do exactly what I’m supposed to do and more.

Well, I’ve been sick with a really sore throat for about a week. I went to work Thursday, Saturday, Sunday, and Monday just like I was scheduled anyways. Today, I had a fever and went to the doctor before my shift at 4 and found out I have strep throat. Therefore, I was told not to go to work because I’m contagious.

So, at 11AM I called and spoke to the manager like I was told to do if I have to call in. I told him what was up and he replied, “Okay, I’ll let them know.” At 4:30, I get a call from a head cashier asking where I was. I told her what happened and she said, “So you called in for the whole day?” Yes, it’s strep, not a flat tire. (Of course, I didn’t say that.) When I told her yes she just said, “Okaaay” in a very doubtful tone.

Now I’m worried I’m going to get in trouble or even fired for being sick. I’m not asking if anyone here thinks I’ll get fired, because I know they can fire me for no reason at all, so I’ll just have to wait until my next shift on Saturday. But I’m starting to feel guilty about calling in, which is stupid because I’m sick.

They don’t take doctor’s notes or anything, so it looks like I’ll be worried all week about it. I can’t help getting sick, and I’m pretty sure no one there wants my infection. It took me over a month to find this job, so I’m worried about losing it already. I’ve never been fired before.

What would you make of this situation? Should I have just gone in?