Dear Sly Blue (a lovely name):
I speak to you as an elder who has lived a long life as a trans-person, and transitioned late in life. So my words come to you from that experience; not necessarily as well informed but simply from someone who walked your path for decades upon decades. I offer you my compassion, hope and listening with the knowledge you should have a full and wonderful life, and one such we here all seek. In your case you are dealing with a mysterious and profoundly transformative condition and period in time early in life - a gift really, a true gift that few ever imagine much less experience.
Just now though, your sadness and despair are understandable and we here get that fully. You have our support and our offering of a deep felt sense of caring. Please continue to turn to us; it's why in part we are here and because we need you too; we all benefit from our sense of community, fellowship and support. I wonder if you might consider seeking out a local support group. You are likely to find others face-to-face who are on the same journey as you (or close enough), and therein perhaps will grow a kindred spirit of adventure, caring and love that is so essential.
Your mom is having an all too common reaction, and her reaction is all about her perceptions of herself and as your mother. Try to keep that in mind as she responds to you, she is on a journey too. In time she may change and what blessing that would be. However, she may not change and that makes your outreach here and possibly to a local support group extremely important.
As for the dread, the grief, the guilt and a broken heart: Many of us in the trans-community know this well and the despair it can lead to including its serious consequences long-term. I am sad to say that I confronted my trans-gift throughout childhood, youth and adulthood always with an eye to the dark side. Then a time came when I looked into that abyss one evening for too long, but thankfully for reasons still no totally clear I wasn't successful in stepping into the void. I learned something quite empowering once on the other side of that terrible moment - if successful I would have never known my true self nor would there have ever been peace . . . and that loss would have been far more grievous than any I could imagine and/or create.
You will eventually breakthrough and know the joy of being whole and complete; it will take time. You are beautiful person who can become a wonderful member in the great clan of manhood. You richly deserve to do so.
Take care and stay in touch,
Rachel