Why are people cruel

I feel like such a failure,

My daughters father and mother are making our life miserable. My daughter is one she was in hospital last year for three weeks with an immune disease. Since then has had constant infections. They have been telling people including the drs surgery that she’s fine and I’m the problem even though her medical records would show what she was diagnosed with and treated for.
I do my best for my daughter and now I’m made to feel like a failure because she gets sick. All kids get sick :sob::sob:
It’s at the point I feel like I should just change drs.
People can be so cruel.