My 4 yo is learning his numbers. He's writing them all backwards (i.e. his 3 looks like a big E). Dyslexia?

My son is in Jr. Kindergarten (3rd year of pre-school) and has been learning how to write his numbers and letters. He practices at school and at home but just recently started writing his numbers from 1 to 7 backwards. Could that be a symptom of dyslexia? If heard people say it is and others say that's a myth (writing backwards). If he has dyslexia, I want to be aware of it and get him help as early as possible. My husband was diagnosed with dyslexia way after he graduated from high school. He had trouble all through school and it's such a shame that he didn't get help with it when he was young. Thanks!