pregnant or late period?

kay
i had protected sex but my period is 6 days late, my boobs have been hurting and I have white/yellowish discharge and today I started getting mild cramps. I took 3 pregnancy test and they all come back negative . My bf says that I'm not pregnant because we used protection and we used it right but idk what to think??? I don't wanna be pregnant yet, I have a 28 window , but this is the latest my period has ever been, I'm always regular , any suggestions ??