Does Birth Control Pill Cause Spotting Or Is It A Sign Of Pregnancy ?

hello, my last normal period started april 20-24, me andmy boyfriend always have unprotected sex. we had sex 3 times in may. i had my last period may 29- june 1. i had unprotected sex june 10th-june 12th, we used the pull out method. we had sex again june 27th 3 times that day usingthe same method. i still havant had my period. i started spotting off and on for ten days now. it started july 1st. i have taken two test they both said i wasnt pregnant . i ve been have lower back pain , my breast have been really sore , and cramping. when i started spotting i started taking birth control , because i thought it was my period, then realized ive never spotted before. could i be pregnant? do i need to stop taking my birth control?