I Have Blood In My Stool When I Go To

I have blood in my stool when I go to the bathroom. It's a few days before my period. I am also starting to have lower back pain which is a similar pain to what I have every month before the period starts. However, i never had blood in my stool before. It's a plum color and does not show when I wipe, it is just in the stool and turns the water red when I flush the toilet. I am really upset and freaking out. Please advise what this could be.