Red/brownish discharge?

So yesterday me&my boyfriend done everything but sex and when I got changed for bed I noticed there was a brownish discharge in my knickers? 
It was the colour of my period but I'm not due until Wednesday.
Then again this morning there was a little of it in my knickers, again the same brownish colour and in a creamy discharge form? 
Has anyone else experienced this before? What could it be? I'm not on any BC and haven't had sex in over a week if that helps. 
Thanks x