Long and very light period

My periods are usually very normal. Recently things have changed drastically. I didn't have a regular period for around 3.5 years aside from occasional super light spotting that I would only notice due to an eating disorder and drug problem. When I finally got help and went to treatment for both issues I started my period again once I reached a healthy weight. My last period wasn't normal at all, I had a very heavy and painful period it lasted around 7 days. SUPER BAD. I wanted to curl up and die. And this period has been super light and it's been ten days now. This period I started using the diva cup. And for all day it only has a tiny puddle in the bottom. Most of it has been very dark occasionally it's been red. I've been having regular periods for around 6 months or so until these last two. I have had an implannon for almost 4 years now and I'm 21.  Is there any reason this could be happening?