Hi Sweetie
Please bear with a bit of bio for context, and I shall answer you. My take on this is different, as I'm in my 40s. Last year I transitioned, and with astonishing good fortune I went from boy to girl in 6 months. My friends and family are wonderfully supportive. And, although I assumed that new friends to our circle would have been told the story, I discovered that this wasn't the case - the newcomers saw a girl, and were surprised when I outed myself. At work through, everyone knows I'm the girl who was once a boy - I am one of the office gossip topics. And to be frank, as much as I knew it would happen, it pisses me off when newly arrived colleagues know.
To your dilemma: I fully undertand the frustration and desire to "come clean" and be totally open about all aspects of your life and persona. It feels good to know that you're not hiding the truth, and there is always some internal stress when you partially recast the history of your life to totally match your gender. I do it; we all do but, if you think about it, all of us tweak our personal histories to suit our needs regardless of gender.
I am going to come down firmly on the side of keeping your past undisclosed. University is a time of of rapidly changing social allegiances, and today's best friend can turn into tomorrow's bi*ch. Looking back at my uni days, I would never dare to disclose something so personal, because there were just too many drunken occasions for things to slip, not only from me but from other people. I extracted astonishing personal information from drunk friends and strangers. I never used it, but I was surprised at how easy it was for them to disclose this, and if so, no privileged information, such as gender history, is safe. For a girl who might have an abortion, or worse, in her past, her story ultimately becomes public knowledge. For young people, who haven't lived much "scandal", anything like this becomes a big thing; older people are more discreet for having lived their own scandals, for lack of a better word, but I suspect that your world is mostly composed of young adults.
The difference between my story and yours is that I cannot hide my gender history - I have 20 years of adult personal and professional life behind me, and it would require a self-defeating effort to do the stealth thing. I don't see a need to disclose my history to people, but if they decided to dig, they'd find the evidence. In your case, however, I think it would be crazy to expose yourself to the risk of gossip and possible prejudice. That doesn't mean you should never tell anyone anything, but you need to be really, really, really, REALLY sure that this information will forever remain confidential. Young adults, sadly, are probably not the best confidants, sorry.
And returning to my initial point, if you recast the story of your life in female terms, so what? You're probably already being more candid about most things than many people. Yes, I agree that transition is a major life event, but you've shared this with some people, so keep it to that group.
I hope some of this makes sense.
Hugs
Julia