CM, even without addiction involved, relationships change and people grow apart and most time one partner is hurt more than the other, that's just how it is.
When you take the same situation with an active then recovering addict and an active and recovering codependent, it is more common as each person finds what they need to grow, or one does and the other does not, and either way the relationship becomes toxic and painful.
You are wise to move on with your schooling and your life, learn from all you have been through and heal, and learn how to take care of yourself so that you do not end up being the person doing all the work in a relationship.
I wish you well and happier days ahead.
Hugs