19 days late for period , not pregnant. Scared

Looking for some female experiences as I’m very scared . I’m only 32 living in Australia . I have suffered back pain for over a year which I’m told is muscular as it hurts with positions like sitting and sleeping . 

I have pretty much skipped my period for the month on September and really scared it’s something bad or related to the pain somehow . 

Google tells me to see a doctor after missed period become regular but this has never happened to me and I don’t think I can wait more months for answers . Can anyone help ? 

Does the pain happen when you have your period or all the time? Where abouts is the pain and what does it feel like?