To be, or not to be pregnant?

My cycle is normally around 28-30 days, but I am 46 days late. YES, 46 days late. ? 

I recently have been experiencing some spotting/bleeding. Nothing close to filling up a pad. It often changes colors. Light red to dark brown , dark brown to tan , tan to red again. Which is really annoying me, because i'm not understanding whats going on. 

I have hopes of being pregnant but I went to a clinic and the urine pregnancy was negative |-O. Im not too sure of how accurate those are.

Please give me advise, what you think might be happening, or share personal related experiences. PLEASE , I need help . 8-|