What Causes Tightness In The Throat?

I have had tightness in my throat x2 days feels like It's going to swell up and close off airway could you tell me whats could be causing this?? I am takling Cardiazm 180mg for svt and I have been eating low carb for about 2 months...I also have had in the past couple of days a stabbing like pain on and off under left rib cage and upper middle part of stomach...