I hope you have gotten help by now, but if you haven't, please call your dentist. He or she should have a pager number. I had to page my dentist the day after Christmas and she called in a prescription for antibiotics and main meds for me.
If not your dentist, then a doctor should be able to do the same for you. Or go to an emergency room or urgent care.
In the mean time, ice water in your mouth can help. Rinse with salt water or hydrogen peroxide mixed with water. And take vitamin C. Drink lots of fluids, and ibuprofen is probably the best thing for the pain and swelling.
If you don't have a problem with aspirin, you could try dissolving some baby aspirin on your tooth and the surrounding area. Or oil of cloves to help numb it.
But I am not a doctor, so you really should find someone to call. Your local pharmacist may be helpful. They have a lot of training.
Good luck. I hope you feel better soon.
Advil, or ibuprofen, is a great anti-inflammatory and will help with pain. Remember not to drink alcohol when taking it. As for infection, chopping up some garlic and eating it raw on a salad or on a sandwich would help. Garlic has been in the news lately again as a wonder worker. It acts like a natural antibiotic and quickly goes into the blood stream.
I understand where you are coming from and have this happen three times. Most x-rays will not provide excellent clarity of a crowned tooth, thus missing the decay. If you are having pain, the tooth under the crown is inflamed, infected and bacteria are usually the cause. Antibiotics may provide some temporary partial relief but will likely not cure the problem. A root canal is most likely needed, and a dentist can do this, but the best is to see an Endodontics, which is a specialist for doing root canals. I believe Crown failures are common after 5 -15 years, simply because bacteria will get inside of the crown and have a field day with your tooth, all the while the bacteria are protected from removal, hidden by the crown. Many Dentists does not communicate this reality when they sell you on getting the crown. An Endodontics can do the root canal without removing the crown, they just drill through the crown, do the root canal and seal entry of the crown. Hope this helps.