You should definitely consult a doctor, just to exclude all the possible physiological reasons, for example diabetes. After that you can consider psychological

You should definitely consult a doctor, just to exclude all the possible physiological reasons, for example diabetes. After that you can consider psychological mechanisms, for example a defense reaction against forthcoming job change and it's requirements (learning new things). It sounds like a stressful situation and your reaction is quite common among people in similar situations. So it's absolutely ok to seek professional help, instead of trying to find a solution on your own.