Blood-tinged Discharge??

Breanne
Hey guys, 
Just going to quickly give a back story - so lately I've been having sex a lot more. And recently I've noticed my discharge is a bit blood-tinged? And I'm not sure if it's something more medical or if it's because of all the sex - occasionally the sex hurts and we stop. A week or so ago my discharged was a bit brown which I assumed was just left-over blood from my period and my body self-cleaning.   
Any idea what it's from?
I'm not spotting or anything. Just a bit of an increase of my discharge and occasionally it has blood in it.
Thanks in advance for the answers.