And like "Let's eat Grandma" shows how punctuation saves lives, this bit of humor from Grammarly shows how punctuation can save love lives too!
I'm sorry I love you = I'm sorry (that) I love you.
You need some punctuation — a semicolon is good:
I'm sorry; I love you.
And a period can also do the same job:
I'm sorry. I love you.
Keep those independent clauses separated!