I take Omeprazole 20mg once a day and have been for the past 13 yrs. All of a sudden it has stopped working, getting bad pain, especially burning in my throat, so I have started taking it twice a day, morning and evening before meals. Still no effect. I did try taking 40mg in the morning instead and that has made it worse! My doc says to persevere taking it twice a day a little longer but usually in the past it has worked almost straight away...........not this time! Has anyone else had problems after taking it for such a long time?