I've had a horrible migraine for the past 3 days and nothing I do seems to help it. I've also had shoulder pain and numbness on the right side of my body. What could this be?

Seek medical help. Have you been in any accident? Lot of time tmd/tmj can be super imposed do you have any ringing in the ears too look up neuromuscular dentistry that might help.
The. The most worrisome thing would be a stroke, also known as a cerebrovascular event. This occurs when blood does not flow to a certain area of your brain due to either a blood clot or a ruptured artery. This is a serious situation and requires immediate medical attention right away. Even if your symptoms are less severe or have gone away by now, I suggest you present to a local emergency department right away for appropriate evaluation, testing, and treatment. Wishing you the best.