I Give Relationship Advice But Am Terrible At Relationships

I'm in high school, recently my girlfriend broke up with me,(I go as a it everywhere because I'm too scared to come out as trans) and we are still friends and it's hard when I can tell she has already moved on after a little bit more than a week. I still love her and I want her back, but today I heard her talking about a new kid and asked if he was hot, which really hurt. And I was sad the rest of the day for band camp. She asked if I was okay a little bit after that, I guess I did look upset, and I blamed it on being tired because I really don't want to tell her that I still have feelings for her because I can see she doesn't in that way. What should I do? And if she does ask again tomorrow I'm going to say "eh..." just meaning I'm not great but not bad... And then if she asks why i think I will have to say I don't want to talk about it. Is that a good idea? Sorry for it being so long