Help me

So my period is really late. I haven't even had it at all this month!

The thing is, I've experienced cramps, and that weird brown/old blood I always get before my period. But that stuff went away and I still don't have my period, which I usually always have after that stuff.

I took a pregnancy test last week and it came back negative. I was relieved, but I still have no period.

Please help??? What do I do??? What's going on????