I'm not thinking, just spiraling

I dont even know what to say here. I just am afraid to talk to anyone I know. I dont want to bring anyone down. I'm not entirely sure why i feel like i just want to die. I'm too chicken shit to do it. My life is a fucking joke though. I'm pretty worthless aside from being domestic and working retail. I'm 36 and My childhood was spent playing mom for my bros and sis while my mom either drank herself stupid or was in jail. One of my younger bros just had to move jn with my fiance and 2 roomates because he tried to slit his throat and after psych ward my family said they didn't feel safe with him there. I'm outa work on medical leave right now and Since this all happened i just feel frozen in helplessness. I cant get started on anything except taking him to and from work. I'm sitting here crying the rest of the time, just thinking how much better life would be without me in it. My fiancé would have the money he needs to live a great life and could find someone who feels his same passion right now, my family would actually figure shit out for themselves. Maybe. I just cant. When everyone is home i try to just get high as a kite to fall asleep so I dont have to be near anyone. Wtf is wrong with me. This happens too much. My brain doesnt make any sense. There are no real thoughts just horrible deadening emotions. What do I do?