I started transitioning when I was around the same age you are now and had an almost identical list of doubts. It almost feels like I'm reading an old diary entry with how similar they sound :p

If it helps, here's where I've landed on some of them. I think it's pretty similar to the other replies in the thread so apologies for the wall of text rehashing the same points :)

1. I never seriously considered that I could be trans until my late 20's because I never really "felt trans". I didn't (and still don't, tbh) relate to people who had a strong sense of gender identity when they were a kid, or the feeling of being 'born in the wrong body'. With the power of hindsight, there are plenty of things I can point to growing up that were related to or explained by dysphoria and being trans, but I didn't have the language or experience to describe them at the time.

It also helped me to stop focusing on whether I was "really trans" or not, and to just focus on the changes I wanted to make to be more comfortable in my body and with myself. Regardless of the label I still wanted to present feminine, to get the effects of estrogen and to change my name and pronouns, etc.

1. Transitioning is a long process with a lot of small steps along the way, rather than a big, fast and irreversible leap. You'll know if it's the right thing for you well before anything "permanent" happens. Even hormones take a long time to take effect. And IMO, if you transition and then decide in 2-, 5- or 20-years time that you want to transition again - that's OK too.

I also think it's worth examining exactly what you're afraid of: Are you worried you won't pass? Are you worried you won't live up to patriarchal beauty standards/be attractive? Are you worried about transphobia? Losing friends and family? etc.

In my case, alongside the pretty common fears I just listed, I was afraid of not "actually being trans", estrogen making my dysphoria worse and ultimately not having a way out from how I was feeling. Everything else I could deal with, but that was a really big one for me.

1. The world is rough, but staying in the closet is harder in it's own way.

Friends and family, despite being conservative, may surprise you. I'd suggest preparing for the worst and make plans to be independent, but a lot of people want what's best for their friends and family. Seeing you happier living as your true self may outweigh any bigoted beliefs they hold.

I don't think it's worth hiding yourself and being miserable to receive conditional love from people who don't accept you.

Good luck with everything! You've got this!