I have someone starting on my team Monday. What have you found helpful on your first day on the job?

Fortunately, I came in around 15mins early and then tried to work normally until around 12:00, but after going to the bathroom 3 times and spending over an hour in total in it, I decided to tell the guys that I needed to go home. The worst part is that besides this one particular, unexpected emergency, I have other health issues that may require more time off for treatment (they don't know about this because I don't know anything either, it's a guess), but thats like a month from now or more. Well what do I do? Because I want to work. For now I told them that I expect to be able to be back tomorrow but will call if it's not the case.

I’m really nervous about working at a new company. got any advice about getting through the first day?