Help 4days Late

Hey ladies, I am currently 4 days late for af... HPT Negative midday yesterday.
I was due af on 14th and ovulated around 29-31st... Dec14th last af started. Me and my fiance always use a condom ( have done since baby born march 11)... Help!! What's going on!!
We arent TTC getting married in Dec!!!!

I have headaches, really aching back and still having stringy-ish discharge sorry tmi!!
My Periods have been like clockwork since having my daughter...

Advice needed!

Thanks in advance!
Lau x

Get a blood test done.