Break through bleeding ?

So the last week I've been having a brown watery discharge. The discharge didn't smell different so I've just tried to ignore it. But today I went pee and wiped and notice bright pink blood. And now I'm worried. I'm not sexually active, I'm on birth control, and when I started getting the pink discharge I went and got a urine test to check to see if anything was wrong and they told me all the test that was ran on my urine came back negative. I m worried because I've been on birth control since April and this has never happened to me. I'm not suppose to get my period until Tuesday