Hello. GI issues  like bloating are expected with duloxetine, so it is advised to take PPI tablet like pantop 40 mg initially for a week till you are accustomed to the new medication. pregabalin can cause drowsiness, giddiness - so one way to reduce that is to take it by 6-7pm in the evening. Donot change your position from lying down to sitting or standing immediately - wait for 2-3 min in one postion before changing. If your body is still not tolerating this medication in 2-3 days, visit your doctor locally and they will consider reducing the dose or  make dulox 20 mg in the morning  after breakfast and pregabalin 75ug  at night 7pm. For back pain relief - it needs detailed examination and opinion - so please visit neuromedicine/surgery for further treatment