I guess I'm confused. You've been together since he was 13 (!) and you were sixteen, and he was sent for intensive treatment THEN because of his addiction, in 2010?
and then...". I already see a psychologist for anxiety and depression which i was diagnosed with a year and a half ago when I first met him. "
At any rate, the world needs good veterinarians. This is who he is today. It's not about abandoning anybody. You will love many people throughout your life. Some will be family, some will be friends. They will have different religions, different philosophies, different attitudes about money and having children. Your friends and loved ones attitudes toward any of those things don't affect you. You life partner's views and actions will.
This is the person he is today. The fact that we love someone doesn't make him/her the right person for us. That would be true whether or not that person was an addict.
I can tell you that in 25 years, my husband never got better, only worse.