What can happen when the blood test show low bicarbonate (sodium bicarbonate) level and high anion gap?

Seek the cause: This can be due to any thing from exercising hard and not being fully recovered, to being in shock, to having some unmeasured anion (aspirin, drank antifreeze, diabetic ketoacidosis), to a variety of other things. Your physician is hopefully competent and can find the cause -- it's one of the most basic workups in medicine. Best wishes.