Anna...

It sounds like you're in labour.
I had my 1st baby recently, and I wasn't sure if I was having 'braxton hicks' or labour (as I had never had braxton hicks pains).
Within hours it went from a twitching back - to agony! (my baby was sitting back-on-back which made it really painful, and resulted in an emergency c-section).

Phone your hospital, and explain the feelings to them.
They will be able to tell you what to do.
Time the pains if you can... as they will ask how far apart the pains come & how long the pain lasts.

Good luck Anna. It sounds like you're going to be a mummy VERY soon!!!