How much do you keep from your significant other about your struggles?

I (38F) have been married to my (41M) husband for almost 20 years. I find that I’m keeping more and more from him, not necessarily out of secrecy, but more out of protection. I don’t want him to hurt, or feel like he has to “fix” me…I’m also slightly concerned that he’ll be angry. I have struggled with self harm since childhood, he thinks it’s infrequent/non existent anymore. I’ve just gotten better at hiding it. Soles of my feet, on my scalp, etc. I struggle pretty severely with SI and I’m pretty sure that if I told him, he’d react very poorly…possibly with anger.