Rejection
Defeat
Bees! - I'm more than sure I'm allergic to them, and I could live my whole life not finding out.
Jellyfish and other scary water animals - I refuse to get into natural bodies of water these days.
Also that I will be unable to have children, or if I do, that they won't be healthy... miscarriage, still birth, if they're ok, I fear them hating me.
My biggest fear of all is dying a slow or violent death - being murdered, trapped in a fire, drowning, falling, being stricken by a long, drawn-out illness
Kinda sad, but there you go, my worst fears.