Sadly not being believed is as old as time. When my Mum was in labour with my big sister (she had had a still birth previous to this) the ward staff sent my Dad in to 'shut her up' as she was making too much of a fuss and the monitor was saying she wasn't in labour. My sister arrived 30 minutes later.
My experience - dc1 - I said I felt like I needed to push, I was grumped at as it wasn't time for me to be examined - but 'oh yes you are fully dilated' dc2 - I was pre-term so being constantly monitored (this was after I had been told that it couldn't have been my waters breaking and I must have just wet myself) and I was told that I wasn't in labour, yep he arrived a few hours later.
I (and my Mum) actually labour in the hip area, so a monitor will never pick up on contractions as they are not traditional ones, I also only had gas and air towards the very end as I managed ok. I am not saying that to be all smug, but to highlight because I don't labour in an expected way I wasn't really believed.