Hi and welcome to the Migraines & Headaches Community.
You don't have to go to the hospital unless it's a life threatening side effect like trouble breathing or throat closing up. You can always call a pharmacist to ask questions about any medications. And they are easier to get a hold of than the doctor usually.
Go to the hospital now instead of waiting 18 hours! If you are having an allergic reaction, you talk with a doctor as soon as it starts, instead of waiting around to see what happens.
What if it is not the antibiotics and something else instead? Are your symptoms going to go away or are they going to remain? Only a doctor will be able to tell you what is really going on.
Hope you get feel better.