Late period

So my boyfriend and I ALWAYS have protected sex, and he's never came in me. We had sex 2 days before my period was supposed to start, and now I'm 10 days late. But the thing is, for the past 5 or so days, I've been spotting. Like when I wipe there will be some blood, as if I was starting my period, but then that would be it? I have taken 3 pregnancy tests and they'll all said negative( like I expected bc we always use protection ) so what could be going on? I'm really freaking out