Well I don't have any experience on this but I'd like to offer you support
. I'd just say don't make it a big deal if you don't want it to define you. I think it's definitely a part of you, but one of those things that personally I'd just answer when the topic came up (i.e. Have any hot dates coming up? Oh ya there was this cute guy/girl that I'm meeting up with). Med school is like high school
, everyone will find out everything anyways if you only tell a couple of people.
It sounds like it's stressing you out because you are making it a big deal.
I'm not trying to diminish the hardships you've faced because of it. I'm more of the opinion that sexual orientation doesn't matter. It's not a big deal I'm heterosexual and I wouldn't want people to define me by just that trait. I'd assume the same is true for you.
Here's one of my favorite quotes that might help you out: "Those who matter don't mind, and those who mind don't matter." - Bernard Baruch