I didn't understand. you are transitioning (eg on hrt) and you didn't have srs yet? or you aren't physically transitioning yet and identify as a woman personally or socially too (ie social transition)?
in either case you can explain them the current position and let them figure out instead of you doing it for them. edit: I mean like saying you are a woman at stage xyz of transition and not asking their sexuality instead.
also online dating can be pretty frustrating at times. I would advise against making it a primary focus or a big source of self worth at any point.