You probably aren’t. You probably weren’t properly taught fractions and decimals. There have been studies that show that the overwhelming majority of, specifically Americans, who say that they are bad at math, just never really grokked fractions and decimals, and so the rest of the language makes absolutely no sense. We have been terrible at trying to teach that specific part of math for decades in this country. I really wish we would adopt the curriculums that are actually working elsewhere in the world at a national level.
My mother is still a teacher in her 80s (substitute teacher so she has something to do in retirement,) and I majored in Computer Science and Music Education, I just quickly found out that education is not a field for men to be in, in this country. Too risky.