I don't know nearly enough about your personal background to make any sort of judgement on to what extent your success up through university came from innate "mathematical ability" versus other factors.
But I do know that making it through a Masters-level program makes you a very capable mathematician, even if were unable to start a career in pure mathematics.
You made it further along in your mathematical education than 99.9%+ of students, and I have a very hard time believing that "biological predisposition" is what's stopping many people from making it past high-school level math.