Maybe say you are spending time with a friend? Or try to come up with some other theme for a youth group that you could say you are going to.
BTW, questioning gender is the right way to say it as opposed to sex.
Best of luck, and if you don't find a way to make it work, there are online resources (though I know they're not the same). I volunteer at a college LGBT center, if you can't find a way to get involved with your local group, PM me and I'll try my best to share whatever other resources I know of.