What Is Real/True?

In high school, I always preferred Math and Science to English and History. My reasoning was this: English and History are products of humanity, which is flawed. Math and Science were discovered; they were always here. How could I accept the rules of grammar, when they seemed so random? I always asked my English teachers, "Why can't you say someone "did good"? The only answer I ever got was "that's just the rule". This didn't seem very "real" to me. Similarly, I found it very hard to really believe my history textbooks- how could I really know that the authors were telling the whole truth? They had to have been biased when they wrote it. Despite my skeptical nature, I never questioned math and science. I really believed (and I still do, so far) that math had always existed; it was simply discovered by humans- not created. However, I am very open to possibly be proven wrong. In what way has math been constructed by humans? Also, I think we tend to value natural, inherent things over the "constructed". Why is that? Is something not true just because it was constructed?