I was incredibly nervous before surgery, as in having to take anxiety meds anxious. And I've been yearning for a flat chest since I was a teenager, and am now 37. I def feel your concerns about scars and how the rest of your body will look - surgery isn't a magic bullet that suddenly makes all body issues go away. I also had a lot of fears about the procedure, etc.
I'm now almost 3 months out and I'm so glad I went through with it. Having a flat chest is amazing - I used to wear so many layers of clothing that it's still very surreal to just put on a shirt and leave the house. It's true that a flat chest can make it seem like our hips are bigger, etc, but I don't obsess over that - lots of cis guys have different kinds of curvy bodies too. Some people will never have a flat stomach or 6 pack, no matter how much they exercise! My partner is a cis guy who runs a lot, lifts weights, and is a little squishy in the middle - plus I have more muscle tone than he does. It's just how our body types are.
Obviously it's impossible to predict how we will feel after surgery, but I think it's important to acknowledge that doubts, fears, concerns, etc. are totally normal and probably healthy! It means we are really thinking and feeling deeply if this is the right decision. I had a lot of fears about scars and had dreams where my whole body was covered in scars, that they were gross or wouldn't heal, that kind of stuff. But from the moment I saw my chest I thought 'oh, they don't actually look so bad', and that feeling has continues. I'll never be one of those guys who walks around without a shirt (I'm just kind of modest), but nothing compares to the feeling of just throwing on that shirt and leaving the house, or exercising in a tank top and feeling comfortable with my chest for the first time since I was 12 years old.
I also used to not like my chest being touched, and felt very disassociated from that part of my body, and that has changed too. It doesn't change for everyone, but for me it's suddenly nice to be touched there. I'll admit, I did cry when my partner touched my chest for the first time when I felt healed enough. It felt deeply healing and so much emotion came up I was surprised, but it felt healing and like a huge release of some deeply held pain. Kind of amazing!
Sending you luck in healing, I'm sure you'll be fine!
-TC