I am ‘real’ with my children because I have to be

You shouldn’t don’t care if other people think you shouldn’t talk to your child about ‘why Mommy cries sometimes or why she can't play with them.’ It’s more important to tell them the truth, that Mommy is sick, than have them wondering their whole childhood and growing up thinking that it their fault. As a result, your children will be more understanding and empathetic than most adults because they realize that sometimes even Mommies struggle with their emotions. This could be a thing to as a mom but it's important to your relationship with your child/children, not to mention as they get older they will be more understanding to other people with the same issues. Just remember you are enough.