Had this happened to anyone?

I'm not sure what's the problem. Has this happened to anyone before?????? I'm on cycle day 51. No period for March. Last period was Feb18th. I Took a test today and it was BFN!!!!! Ive been alittle nauseous. I've been extremely tired. Stomach cramped alittle a couple days ago. And I've had very heavy cm. I was thinking it was AF but every time I went to bathroom and checked underwear it wasn't AF. Just had ALOT of cm. can someone please tell me this has happened to them and they were actually pregnant????? I just need answers. I just need HOPE!!!!!!