Help!! Spotting for 3 weeks

I’m kinda freaking out. I’m 21, and don’t know that much about any of this I just know I had a normal period at the beginning of January and since the beginning of the third week in January I’ve been spotting and it will sometimes look like normal CM but most days it’s brown or reddish I’ve also been cramping supper bad and lower back pain. And the pain is constant. I have had multiple partners the last couple months and I’m on a low estrogen pill. And still spotting!!