Over the last couple of months, my cycle has become very short. Last month my period started 21 days after the previous one, this time 18 days. I also had one month last year when it was 18 days, but everything went back to normal. I even went to the doctor cos I found a lump in my breast in what I thought was mid cycle to realise a couple of days later it was just premenstrual stuff.I have always been very 'regular' until recently. Has anyone else had a change like this, know why it might happen. Is it something I should be worried about, see the doctor about, do you think?