I Left A Tampon In Too Long I'm Not Sure

I left a tampon in too long I'm not sure exactly how long but I know it must have been over 12 hours at least ....my period lasted for almost 2 weeks yes 14 days and just stopped 2 days ago now I'm having ovary pain , really really bad headaches , and lower back pain. I do not have a fever I'm going to the er soon but I'd kinda like to know see if I can figure out what it is and possibly help anyone else who gos through this