Need help admitting probs with fiance

Hey. So I am disabled and suffer from really bad back pain and have for the last 4 yrs.. when I was younger I used to self harm and at one point was suicidal. I told my fiancé this when we first got serious and he told me that he always wants to know if I'm feeling like that again but when I go really depressed two years ago and told him I was feeling suicidal he got really angry and does every time I mention anything close to that topic... I've been feeling like I was to self harm again but don't know how to tell him :/
How should I tell him... I'm so scared that he'll be angry and I'm already feeling ashamed and guilty for feeling this way in the first place