I'm on the progestrone only pill and have been since November last year. Since being on the pill it has made my periods a little more regular in that now they are roughly every 2 months, before they were very irregular (4 weeks, 6 weeks, 9 weeks etc). My last three have been exactly 2 months, this one is now 6 days late. Should I be concerned? Or is it normal as my periods are irregular? I have had experienced tiredness, breast swelling and soreness and 'period pains' (although not quite as bad) for the last week or so. Some of these can also be linked with pregnancy so I'm just concerned that there may be a chance I am pregnant. I have not missed a pill, although I understand that it is not 100% effective.