Given your history, it sounds unlikely that you'll regret transition. Growing discomfort post-puberty is common is transgender people and uncommon in cisgender people -- we're all awkward during puberty, but that's not what you've described. And as severe as your depression has been, your mom's attitude sounds a lot more like denial than an honest and informed evaluation of your expected outcome.
So yeah, people de-transition, but rarely. If you're nervous about that, don't look at surgery* for the time being. If you take testosterone, there's only one irreversible change: your voice will deepen (this is potentially surgically reversible) . Also, you'll grow a beard that will never go away, but that's what electrolysis and laser hair removal are for (expensive and painful, but not impossible). There's some wisdom to "real life experience" requirements -- if you're at all worried about de-transitioning, it's easier if your transition has been purely social and not medical.
* bias alert: I'm personally opting for a HRT-only medical transition. I don't want surgery for myself. You may be different and that's okay.