tenses: what's the difference between the following sentences

I am reading a novel named Thirteen Reasons Why. And there is a sentence (And that's when I realized how hard I had been crying) in a paragraph as follows:

When someone finally did answer, I sucked in the tears that wet my lips and told them that on the corner of Tanglewood and South... But she cut me off. She told me to calm down. And that's when I realized how hard I had been crying. How much I was struggling to catch one good breath.

So my question is: If I change the tense of the sentence "And that's when I realized how hard I had been crying" in this context to "And that's when I realized how hard I WAS crying," Will it make sense and what the difference between this two sentences?

Thank you very much for your time and help!

In normal (present tense) conversation, the difference between "I have been crying" (perfect tense) and "I am crying" (simple tense) is that the former is ambiguous as to whether or not you are still crying.

The novel being written entirely in past tense, this distinction holds. "How hard I had been crying" does not indicate whether or not you were still crying, but "how hard I was crying" indicates that you were still crying (as of the point in time being described).