If you go to the doctor ahead of time and gets a doctor note for excusing me for the next day for rest ?

I have been working with this company for almost 2 years I had 2 call off sick days and I haven't been feeling well at all. I was gouging to go to doctor before hand to get a excuse for the day but I was wondering if its a good ideal. I never been late always here 5 times a week and I work as a part time employee I came in work with bronchitis and everything but this time I'm in really bad pain