Can I make Aliyah if my great great grandmother was Jewish?

My mother’s mother’s father was the son of a Jewish woman from Poland. Though my mother and grandmother and aunt and uncle deny it. And my great grandfather was a bomber navigator for B-17s in Europe so hid his heritage as a catholic. When I read his journal detailing his life he mentioned his mother was Jewish. The only thing my grandmother and everyone else, but my father and myself who read it carefully saw the words describing his mother as Jewish, say she just spoke Yiddish. I would like to know in my scenario could I make aliyah under the Law of Return? I have been feeling this call to go for years.