thanks littlebirdy and feralfox, i'm waiting to hear from my midwives so hopefully i'll be able to stay with this practice, i like them so much!
eleuthia, as aimee mentioned, your uterus will clench up and get really firm. mine seem to vary in intensity a bit too. and sometimes i feel a wave-like motion, as the muscles start to clench up. not any pain, just tightening. once it starts (if it even does) happening to you, i think it'll be pretty obvious, at least it was for me.