In labour one min then not, how can this happen?

I'm currently 38+4 wks pregnant with my 5th child I've never had this experience so dunno what happened. On Sunday I started getting contractions we timed them over 2 hrs and confirmed they were 4-5mins apart we went to hospital the did an internal confirmed I was 3cm dilated and the baby's head was engaged they put me on a monitor and confirmed my contractions were 4.5 mins apart they then told us we'd be definately going home with our baby. As my contractions were still mild they said it might be a while after couple of hours they started getting stronger everything seemed ok and staff were convinced all was underway then over the next few hours the pains got less and longer apart by morning there was hardly any. A doctor came felt my stomach said my uterus wasn't contracting I wasn't in labour and could go home! I've never had this happen so am confused the nurses said it was real labour not Braxton Hicks contractions but why did it stop? I've never been in this position and am so disappointed and confused has anyone else had something like this happen?