Is it normal for the skin to turn really red when u start bp?. Redness that lasts a few days like? ..cause i duno whether to continue using if its always gona be like that. I duno if im allergic to it or if its a tolerance thing.. maybe after a week it will be ok?

Ive been prescribed bp to be used in the mornings .. and differin at night.

Yes, it's normal to experience some reddening of the skin, dryness, and flaking while your skin adjusts to BP. These should subside gradually as your skin adjusts.