1. because you worked in 110+ weather causing excessive sweating
[Non-renal loss] which is one cause of low potassium, likewise check for Magnesium values also.
2. The manifestation of hypokalemia are mainly neuromuscular and cardiac.
3. Take Oral potassium supplements and potassium rich diet: banana,papaya, cheese,tomato,soyabean,coconut water,fruit juices,spinach,potato, chocolates, leafy vegetables.
PS: Electrolyte abnormalities do not typically cause difficulty breathing
, sometimes very low calcium/low magnesium/low phosphate levels can be associated with muscle weakness
which could affect the diaphragm causing shortness of breath
and prickling sensation in chest.