Hi Linzey, I currently went through were similar situation. In past 8 months, by boyfriend relapsed 3 times. My life became hell.
It's hard to let go, but it's for the best. Do yourself this favour.
In my case my bf relapsed in following order:
1. Relapse for a month and quit cold turkey. Promising this was one time thing.
2. Within two months massive relapse where I was worried he overdoses, he tried to kill himself. This was followed by me kicking him out of house. His reaction was to get massive amounts of pills and methadone! Enjoy one "last" night and go psych ward. He was there for 14 days, got prescription pills and seemed normal. I let him back home where he was doing well (including gym) for a month.
3. After that he relapsed and went living as homeless. I thought I will only get to hear of him when he dies. Constant worry where he sleeps, is he ok, etc. I wish I would have broken up with him time ago.
Now he moved to different country and has great job. He wanted me back but I am way too scared and I took my chance to be alone and continue my life without being paranoid.
I hope this helps you to be happy what you have now. I know it's hard to believe it after so many years and just let it go. Take care and stay strong