What’s could possibly be going on?

I’m 16 days late for my period, however I’ve taken numerous pregnancy tests (and different kinds) and all of them are negative. My husband and I use protection, so I can’t imagine there being a way to be pregnant (even though sometimes it finds a way). I’m not fatigued, my breasts aren’t sore, I’m not moody, I feel normal.

I’ve been cramping the past two days, but I’ve still not started my period. Has anyone had this issue? If this continues another week I am definitely going to go see a doctor but I’m trying to see if this could be a serious issue or if someone has experienced something like this before because I would really love some advice.

Thanks in advance you guys!