TD, I think the level of hormones is so low that it won't necessarily regulate (plus it's only progesterone, not oestrogen as well). I have heard of it stopping AF all together, and definitely it seems to cause lighter AFs. But not necessarily regular. I spotted for about the first 3 months, then I got semi-regular AFs. Give it some time to settle down and see how you go then. You definitely shouldn't worry. Have you had your 6 week check up yet?