I really feel for you, I do. I have had to hide the same from my husband and one night a few years ago he witnessed me bashing my forehead into the wall after an argument. I wanted very badly to die and just wanted to stop the pain, I know that's how you feel too.
He is still here. He has seen the good, the bad and the ugly from me and still holds me tight when I'm upset. He's the only one on this entire planet that really gets me, as I'm sure the same is true for your husband. This will be a tough time for him but I am quite certain that after 18 years of marriage he won't turn tail and flee at the first sign of you being in serious crisis. He should understand that he needs to be there for you the most right now because things have gotten this way for you.
You will feel better knowing this is in the open and I wish you the very best in your recovery, it takes time but all wounds heal with tender love. His love will be your light through this dark time.
(apologies for the weird wording, my thoughts are coming across as metaphors and stuff)
If I may ((((((((((((((((((((((((((HUG)))))))))))))))))))))))))