Spotting or pregnancy??

Hi all!

So i have been spotting on and off for about two weeks now, my period was supposed to arrive 3 days ago, so I’m now 3 days late and i do now know what to do. I have been told not to take a test until 5 days late, but if it isn’t pregnancy what could it be? I’ve been on birth control since i was 14 and switched back over to the pill in February and haven’t had any irregular spotting or bleeding the entire time. I need advice lol my fiancé and i have had sex but he has claimed he doesn’t believe he has came in me soo