Persistant Vaginal Discharge After IUD Insertion

I had an IUD inserted in November, then about a month later a little before my period started, I had some brown spotting which I mistook as just the beginning of my period, however I continued to get brown discharge and it became thick a thick mucous and with some pink spotting at times and there was some lower abdominal pain.  The doctor told me I had a slight infection and cervicitis, and prescribed doxycycline me for a week and finished it about two weeks ago, and the symptoms seemed to get a little better and the discharge was liquid, however I still continued to get discharge and some pain in my abdomen.  I just had my period last week around Wednesday or Thursday and after it ended I still continued to get the strange discharge however it has become darker and today there was dark pink liquid with it.  The pain in my lower abdomen has become worse and is usually centered around the left or right side.  Both my partner and I are monogamous and we have only been with each other.  Can someone please help?  I'm really worried about this