Late over and over!?

So for the past couple months my period has been late but always shows up at least after 8 days past due. Well it’s now been 12 days and still nothing! I’ve been having a lot of fatigue and diarrhea for the past month as well as a lot of headaches last week. Thinking this was my period symptoms I ignored it. Well Monday I went for a check up and they took a test saying it was negative. Not sure what to think now. I’m blaming my lack of exercise and bad diet.

COULD THAT BE ALL THIS IS?