I have never experienced this before so am hoping to find out from any ladies who have - what it all means??

I am on CD15 and am having bleeding today. I have not had mid cycle bleeding before and know that after googling it is supposed to be normal (well most sites say it is) but as its a first for me it is still very strange and concerning. I had O pains about 2/3 days ago and have been busy DTD this whole week ()...

I am wondering whether it could be :
a) due to ovulation - drop in estrodial
b) due to some recent vigourous activities
c) a beautiful sign of something wonderful....
d) any or all of the above!
???

any ideas??