Cramping before period? :/?

so here's the deal... ive been taking birth control for about 5 months now. i started my last pack late by one day and then took 2 the day i started. do you think i should worry about that? this week i had exams for school and when i get stressed sometimes i get acid reflux and i have had really bad gas pains and acid reflux. Now that has stopped because im done with school and im supposed to get my period in 4 days and im experiencing cramps. is this normal? also, ive had thick white discharge but ive had some itching..like i have a yeast infection so idk if that's what that's from (tmi) am i pregnant? should i not be worried or should i....is it normal to cramp 4 days before a period? im so scared im only 17 helppp :/ also ive had but im on the pill and he never c**ms inside of me...idk please help.