Yes, Claire, Mary's right. Ring the hospital switchboard and ask to speak to a m/w. Don't take any chances because if you are in premature labour (which is what you're worried about), they can sometimes stop it if you go in early enough or at least administer steroids to helps the baby's lungs etc.
Even if the baby's not on his way, the sooner you get anything that resembles labour checked out, the sooner you can stop fretting!
Let us know how you get on. 'Hope you feel better soon.
xxx