Bump... I don't have that much experience (I've only been through labour once) but what you describe does sound like labour. Congratulations. Don't panic. Do the things that normally keep you relaxed. What helped me to keep calm was to imagine seeing my baby at the end of it. If your contractions start coming every 4 minutes get yourself to hospital. Good luck!
Sounds like it to me! You could ring the labour ward and let them know, but they won't want you to come in till contractions are 4 mins apart, which can take ages to get to! Good luck, and keep timing those contractions!