I've always added the comma without doubt until someone recently told me I'm wrong to do so. What say all of you?

Also, what if I want to say, "Oh, no, Chris! You're bleeding!" Comma or no comma after, "oh," please?
"Oh no!" is an exclamation of dismay. Don't use a comma.

But "Oh, no, Chris, that's not the problem at all." Do you see the difference?
oh, no = oh ......... no

oh no= ohno
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So, are you saying that is correct with or without a comma, depending on the intended meaning? I'm sorry, but I don't quite understand!
 BarbaraPA's reply was promoted to an answer.

Oh, Savannah...I love you!

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Then what about without the word "Chris"?

Would it be written as "oh, no, that's not the problem at all"?