I'm confused...

I may be asking a really stupid question here but I am quite worried..
For about 4 months my periods had been in a perfect cycle coming literally every 28 das but last month's came two weeks late...I presumed it was cos of exam stress cos I had had my A levels, anyway, it was two weeks ago when I came on, and today, when my period would have normally come in the cycle it was going in before my exams, I think it has done, but with only a two week gap since the last time?
Is this normal? Have I got some terrible disease?
Also it seems much lighter than normal but there's no way I can see that I have torn anything which could be causing bleeding........
I bet I look really daft now but any thoughts would be much appreciated!

It will have just been stress delaying it last month.

Its lighter because the lining that sheds causing the bleeding has had less time to build up.

It'll just be settling back into the norml pattern and nothing to worry about