[AJR12345]

My period finished on Day 8 (heavy on day 1-3 then spotting day 4-5 and then heavy day 6 then spotting day 7-8) and I'm now on day 15 of my cycle. I have been having a strange discharge for the past 3 days along with a lot of mid-lower back pain. The discharge started pinkish with a small streak of red mucous(thats how I can describe it best?) while wiping in the washroom and now it is a thicker dark brown discharge that leaks into my Underwear leaving a pretty substantial stain. Just wondering if this is normal or if it is something that should get checked out?