Help a clueless girl out!

I’ll make it simple, I just need advice!

Symptoms: very thick dark brown discharge 10 days before period due

- EXTREME fatigue

-No period on due date (not sure if the thick brown discharge was period or not!)

- sore breasts!

-Mild nausea (on and off)

I know these are signs of pregnancy BUT are they also signs of other things? Anything I should be concerned about