Nothin' Like Some Grammar In The Mornin'

How's your grammar?

I admit, I'm a stickler about grammar. Grammar and spelling. I imagine that's more common than not with writers. Agree?

Getting it all correct when writing is easy enough, but sometimes I hear poor grammar come out of my mouth and I cRiNgE. The offenses are harmless enough, like

There's two in the refrigerator, when in fact, we would not say There is two in the refrigerator.

or

You can go downstairs when me and Sister do. But if you were to take Sister out of the equation, you'd not say You can go downstairs when me do.

I do think these are common mistakes, but why doesn't proper grammar flow in my speech as well as it does in my writing? It makes me feel less validated as a writer. Like people are going to hear me talking and think She's a writer? But she doesn't even speak properly!

Do you have similar trouble?