Hi, it could just be that you ovulated later this month making this a long cycle. The later you ovulate the longer the cycle is. Stress can delay ovulation, to give an example : if you normally ovulate on day 15 of your cycle and you had lots of stress at that time then you might not ovulate until day 25 , if you have a luteal phase ( which is the number of days from ovulation to period) of 15 days then you would end up with a cycle of 40 days! Your luteal phase does not vary much from cycle to cycle but the number of days up to ovulation can. HTH and it is not too boring
Sorry to throw a spanner in the works but I tested positive 20 days after my normally clockwork AF was due, after numerous negative tests. It was awful not knowing, in a state of limbo and spending hours on forums wondering what was going on. However now I am sat here feeling sick as a dog and 11+3. Scan next week and I'm curious to see if there was a reason for getting such a late positive test.
tethers, sometimes you do just have a longer cycle than normal. Mostly it's cause by ovulating late (often stress or illness when you should have ovulated will do this) or just not ovulating at all. It's utterly normal, even expected to have an anovulatory cycle (one without ovulating) every now and then and without the hormones/egg to trigger a bleed, it can mean a long cycle. As you've already discovered, the time between ovulation and your period is generally fixed so if you ovulate late, you bleed late. Likewise, if you don't ovulate at all, your body can just amble along in limbo for a while. If it continues, the GP can help with getting you back to square one.
Of course you might also be pregnant and it's too early to show up just yet.
I wouldn't panic though, it's really common as a one off.