How can I make sure I (a white male teaching math) am sensitive to "underprivileged" students in my class?
First I want to say that my answer does not depend on your gender and race, which I consider irrelevant. I will answer the question in two parts, one relevant to any field, one to mathematics. I suggest changing your title to something like: "How can I show respect to students from different backgrounds?"

General Answer

Understand that your students have had different experiences, which will affect how they perceive your and others' behavior. For example, the phrase "Can I help you?" may be perceived positively by someone who is used to others' wanting to help them, but it may be perceived negatively by someone who has had that phrase used toward them in a hostile manner (e.g., by a retail worker who follows them around to make sure they don't shoplift). I would encourage you not to think that the former student is rational and the latter student is irrational. Everyone generalizes based on past experiences. I encourage you to attend any diversity training offered at your institution or read about microaggressions, phrases that might be innocently meant but negatively experienced.

Be aware that everyone, including you, has unconscious biases, picked up from the cultures you've lived on. You should be aware that most elementary school teachers, regardless of gender, call on male students more often than female students. You may find it interesting to take an Implicit Association Test, although you should be careful making inferences from it.

Encourage students to give you feedback about how to improve your teaching, especially this aspect. We have the option of adding our own questions to course evaluations. I added to mine: 


  What could the instructor do differently or keep doing to make the
  course feel inclusive to students with a variety of backgrounds,
  learning styles, and  mental or physical abilities? This would be a
  good place to mention any micro-aggressions.


Mathematics

This goes beyond what you asked, but I encourage you to learn about stereotype threat, a well-documented effect in which evocation of stereotypes affects students' performance on tests and other high-stake assignments. For example:


  Spencer, Steele, and Diane Quinn, PhD, also found that merely telling
  women that a math test does not show gender differences improved their
  test performance. The researchers gave a math test to men and women
  after telling half the women that the test had shown gender
  differences, and telling the rest that it found none. When test
  administrators told women that that tests showed no gender
  differences, the women performed equal to men. Those who were told the
  test showed gender differences did significantly worse than men, just
  like women who were told nothing about the test. This experiment was
  conducted with women who were top performers in math, just as the
  experiments on race were conducted with strong, motivated students.


Read articles about inclusive pedagogy, especially as applied to college-level mathematics. I have been told that active learning techniques benefit all students but disproportionately those from underrepresented backgrounds.