Is this normal? Being a mum.

I am a mother of a toddler and a 3 month old, I am in constant fear that something bad will happen to them, I am a helicopter mum. I keep having these horrible thoughts in my head, like visions. I am wondering if this is normal? Do other mums have the thoughts of bad things? I am just trying to be the best mum I can be but sometimes I feel like they would be better off without me. I do blame it on my childhood, my parents were alcoholics so they was never at home and when they was, me and my brother would get abuse so I think I tend to try too hard with my children because I don't want to be like them. My mum died just before I found out I was pregnant so that doesn't help. In 2016 I nearly lost my life to sepsis, I was in ICU for over two weeks so I think I am dealing with a lot of demons I need to get over but it's destroying me, I need to be positive for my kids but I am struggling.