What does this mean?

Ty

Haven't had a period in 5 days! I was supposed to get my period 5 days ago, and I have never missed a period. It usually comes on time every month, but this month is different. I've only had brownish spotting for the past 5 days and not an actual period. This has never happened before, and I've been taking pregnancy tests, and they've all been negative. Has this happened to anyone? I don't know what to do.