Disclosure of sensitive information like this is always so damn tricky. I have many a times felt obligated to explain honestly to someone why I haven't been behaving reasonably. Does it actually help in the long run? I don't know. I do know that I am able to let go of a lot of guilt and emotional stuck-ness when I know that the other person's head isn't going wild with speculations of why I am so irresponsible and frustrating to be around. It can also act as an externally reinforced check on my own behaviour, now that the conversation has been put out there, I would be compelled to reevaluate myself more carefully before acting out and behaving in a way that I might feel uncomfortable about again.
Do whatever works for you, in the least distressing way possible. I spent a week agonizing over a disclosure not long ago, trying to start several times and then failing, but one day it sort of just came out randomly.
And good luck.
