What should I do?

I'm one day late, I tested BFN about four days ago.
We only BD once after a positive opk this month as we were having a rest from ttc (I think you guys know how stressful it can be)
I'm never really late, I don't really feel pregnant either.
A little lower backache over the last 2/3 days, pinching pain around left ovary. Boobies are a little sore but nothing mega.
Should I buy a test or just sit and wait and see if AF turns up? 
I really don't know what to do? 

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