In most cases:
I have to text you again = I already texted you, I need to text you again, I haven't texted you again yet
"I've had to text you again" sounds a bit unnatural, you should replace it with "I had to text you again" meaning = I texted you once, I needed to text you again, I texted you again, I don't have to text you again anymore.
If it's too confusing just remember had=past and have=present so I have to is present and I had to is past