How do I (or should I) try to draw out my possibly transgender child to confide in me?

I'm a divorced father with sole custody of two kids, one being in elementary school and one in middle school. My oldest, who was born female and is still referred to by family/etc as she/her, has for the past year or so shown signs of wanting to present as male or hide her developing form: preferring short hairstyles, wearing loose clothing, and wearing multiple sports bras. That being said, she has not made any announcements about gender to myself or members of her family.​I periodically monitor her texts/social media/etc for bullying and so forth given her age, so I do know that she is instructing friends to refer to her as he/him, and even to refer to her by a male name. I have not confronted her with my knowledge since I'm not sure that's the best way to begin a dialogue. Additionally, I'll admit that I may be overprotective given that I'm a single dad, and I know that I sometimes parent from a position of fear because I grew up in an abusive household and I'm very concerned with making decisions or acting in a way that could 'screw up my kids'.​How do I draw her out? How do I refer to her gender/what pronouns to use when she hasn't confided in me or provided input? How should I address her wearing multiple sports bras...I know that can be unhealthy, so should I push the conversation out of concern for her health? I feel awkward with my 'secret' knowledge and like I'm creating an environment where she won't feel comfortable talking to me, but I don't want her to hide things from me, and I'm not sure that I want the conversation to start from "I was going through your phone and accounts and noticed..."​To be clear, my goal is to support her in any way I can, not to judge her or try to change her. via /r/Parenting https://ift.tt/2YO88XR