I know, the age old question 
I already have a two year old but I was induced so I only know what super powerful, unmistakable contractions feel like.
I'm 39+2. For the past few weeks have had very uncomfortable Braxton hicks, period pain type cramps and two "stomach bugs" of vomiting and diarrhoea - but since they were in the same week I suspect they were my body gearing up. Today I went on a three mile walk mostly uphill. Since being home I've had irregular pains in my lower bump - but I don't know if they are the start of something niggles, or just pelvic / ligament pain.
Can you describe how it was for you if you went into labour naturally but didn't realise for ages? I appear to be clueless 