What Causes Thick Brown Discharge After I Complete My Periods?

I am a 26 year old mother of 3 the youngest is 15 months old. Since my last c-section, ive had a thick, brown, sticky discharge about a week after I finish my period. It lasts about as long as my period. Also about 3-5 days throught the month, my insides feel "jumbly". Like everything is floating around In there. It is kinda painful, especially when my husband and I are intimate when its a jumbly day.