Is there any pattern to them? Does it happen only during a certain season? After eating at a certain restaurant?
I'd wonder if it's an allergy to something you're eating or being exposed to. The next time it happens, write down everything you've done, all the places you went, and everything you've eaten and drank for the past 24-48 hours. Headaches, mouth numbness is a symptom of an allergy, and swollen gums can be, too, especially food allergies.
I'd worry about a cardiac arrhythmia with the pain between your shoulder blades, but you have no other symptoms - no shortness of breath, no chest pain, etc. Do you ever get dizzy? You should get this checked, though, to make sure you don't have one. That's really important.
I hope someone else comes along to chime in on other possibilities, too., and I hope you feel better!